With the deepest love To my father Sante and my mother Onorina, To Rosanna, Jacopo, Alessia, Maria Vittoria, my family
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With the deepest love To my father Sante and my mother Onorina, To Rosanna, Jacopo, Alessia, Maria Vittoria, my family
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With the deepest love To my father Sante and my mother Onorina, To Rosanna, Jacopo, Alessia, Maria Vittoria, my family
The Vertical Dimension in prosthesis and orthognathodontics Integration between function and aesthetics
R. Slavicek and S. Sato
Original title La dimensione verticale in protesi e ortognatodonzia. Integrazione tra funzione ed estetica © 2016 EDRA S.p.A. All rights reserved. ISBN 978-88-214-3959-9 Editor in Chief: Costanza Smeraldi Senior Editor : Alessandra Mutignani Production Manager: Paola Sammaritano Cover: Paolo Ballerini © 2017 EDRA S.p.A.* – All rights reserved eISBN 978-88-214-4373-2 No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Knowledge and best practice in this field are constantly changing: As new research and experience broaden our knowledge, changes in practice, treatment, and drug therapy may become necessary or appropriate. Readers are advised to check the most current information provided (i) or procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of the practitioners, relying on their own experience and knowledge of the patient, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the Editors assume any liability for any injury and/or damage to persons or property arising out of or related to any use of the material contained in this book.
Edra S.p.A. Via G. Spadolini 7, 20141 Milano Tel. 02 881841 www.edizioniedra.it
(*) Edra S.p.A. fa parte di
Nazzareno Bassetti C.D.T., D.D.S., M.Sc. High school diploma in Dental Technology (1982), graduated with honors in Dentistry in 1988, from “La Sapienza” University, Rome. Post-graduate training courses in various branches of Dentistry. Post-graduate University Course in “Therapy of Masticatory Organ’s Dysfunctions” with Prof. R. Slavicek, S. Sato and N. R. Mehta, 2002. Master of Science (M.Sc.) at the Donau University in Krems (Austria) in “Therapy of Masticatory Organ’s Dysfunctions” with Prof. R. Slavicek, S. Sato and N. R. Mehta, 2002. Master Course at the Donau University in Krems (Austria) in Orthodontic Therapy in dysfunctional patients with Prof. S. Sato. Title of Academic Specialist in Orthodontics achieved at the Donau University in Krems (Austria) with Prof. S. Sato, 2007. Lecturer for the Vienna School of Interdisciplinary Dentistry (VieSID)’s courses. Acknowledged as national and international teacher of Gnathology, applied from a multidisciplinary perspective. Private practice in Ascoli Piceno, with a main focus on Orthodontics, Prosthetics, Implantology and Complex Rehabilitations with a multidisciplinary approach.
Summer School 2015 Vienna
Dr. Nazzareno Bassetti’s passion for “dental medicine” has led him to refine his technique and preparation over the years, and not to abandon the path of training and study, while constantly continuing practicing. We met each other as the result of a strong common interest about dysfunctions and therapies of the masticatory organ: it has been exactly this same interest that since 2002 has pushed Dr. Bassetti to attend our master classes at the Donau University in Krems and to obtain a further Master degree in Dental Science. Therefore, Dr. Bassetti has begun to apply theoretical concepts suitable for both the fields of prosthesis and orthognatodontics to his daily dental practice; during these years, he has also meticulously documented all the cases treated following our approach, that is to say the VieSID (Vienna School of Interdisciplinary Dentistry) approach. To date, Dr. Bassetti is among our most valuable and worthy collaborators because he shows the real possibility of a successful treatment for complex cases requiring a multidisciplinary approach, trying to spread throughout Italy and abroad his large record of cases and his vast documentation. This book witnesses a very precise professional intention, which makes use of an individualized diagnostic and therapeutic process, finding in vertical dimension and mandibular repositioning the two keys to restore the ideal combination of aesthetics and function of the masticatory organ. Besides being fully detailed, the case studies presented in Dr. Bassetti’s book are also accompanied by a complete set of pictures (around 700) describing step by step the chosen therapeutic path. Finally, we are delighted to highlight that Dr. Bassetti’s work - which translates into practice the theories developed by the Vienna School during the last fifteen years - has achieved the pivotal result of stable therapeutic success in the medium and long term. Prof. Dr. Rudolf Slavicek Prof. Dr. Sadao Sato
Preface The most widespread trend in complex rehabilitations is the aesthetic evaluation; however, it is subordinated to the function, which is the decisive factor for a successful therapy and for the patient’s health. This book describes an integrated operational path, essential for the management of the vertical dimension according to linear and repeatable criteria. It takes into account primarily the function and thus creates an aesthetic result that comes as a natural consequence. It will be shown that each successful therapy made on the patient is always the result of a precise diagnostic flow and of a subsequent therapeutic project, predictable in each of its phases. This is crucial when it comes to health care. Stress and parafunctions related to it (bruxism and clenching) are exponentially increasing, especially in young patients, causing considerable damage to the stomatognathic system. Whether the aim is the correct reconstruction of occlusions in patients with severe problems of this kind, a correct management of the vertical dimension and of the function becomes decisive. Throughout this book, the close relationship between a successful implantology and the implant placement guided by gnathological function, which appears as an often underestimated aspect, is treated instead with an adequate consideration. The text is addressed to all the operators dealing with oral rehabilitations, such as orthodontists, prosthodontists, implantologists, dental technicians, since for all of them a reasoned gnathological evaluation of the interventions to be carried on the oral cavity results fundamental. Finally, the book clarifies a number of controversial points of complex rehabilitation: it will explain how to handle the vertical dimension and all that is related to it in accordance with the practical translation of the Vienna School, headed for more than thirty years by Professor Rudolf Slavicek. Clear steps are illustrated, the ones the technician and the clinician have to follow in order to achieve individual occlusal surfaces, which take into account the function, so as to obtain a natural anatomical shape of the tooth. As a matter of fact, in the treatment of a complex case, it is necessary to reposition the jaw in three dimensions and to establish the position of the teeth within the functional space, obtaining an occlusion capable of stabilizing the reached position and of controlling parafunctions, thus avoiding the risk of recurrence. If it is true that today we are more and more intervening on complex cases to be rehabilitated with a multidisciplinary orthodontic and implant-prosthetic approach, it is necessary to support the transversality of gnathology to all other branches of dentistry: without this premise, we reach out to treatment failure. Nazzareno Bassetti C.D.T., D.D.S., M.Sc.
Acknowledgements Professor Slavicek and Professor Sato have radically changed my professional life: I am grateful to them for their kindness and humanity, for making me feel a colleague rather than a student and for having offered to me the great opportunity of becoming a teacher of their courses. I thank my friend and collaborator Emanuele Camaioni, with whom I shared many cultural experiences, for making available to my ideas his undisputed expertise in dental technology. There are many other friends and colleagues that I would like to thank you for having contributed to my professional growth. Without Milko Bufalini, Giorgio Chiogna, Eugenio Tanteri, Markus Greven, Christian Slavicek and Guido Garotti, my whole path in the planet of gnathology would probably have been less exciting. I thank my former student and current friend Dr. Simone Gismondi, who embraced with great enthusiasm my modus operandi, encouraging and supporting my dream of writing a book to witness and tell the last fifteen years of my work. A special thank you goes to my patients, including my niece Luna, for their availability in letting me produce an accurate documentation of the treatments to which they have been subjected; a special mention also to Silvana and Giulia, my chairside assistants, for their meticulous professionalism and for the patience they support and accompany my work with. A heartfelt thanks to Dr. Francesco Simoni, who works for Odontoline and who first believed in the possibility to implement this project, to my publisher EDRA and to Dr. Alessandra Mutignani for having turned it into reality. Finally, a special thanks goes to my wife Rosanna, for the patient and invaluable revision of the text.
Table of Contents CHAPTER 1
Transversality of gnathologic principles Introduction Thinking gnathologically Patient classification for a standard diagnosis Therapeutic risks’ reduction and control Main patient requests Looking for signs and symptoms of cranial-cervical-mandibular disorders (CCMD) How to intervene? CHAPTER 2
Analog and digital gnathologic diagnostic flow Introduction Clinical and instrumental analysis 1 From the impression to the diagnostic model Face bow and mounting on articulator of the upper cast Reference wax and mounting on articulator of the lower cast Photographic documentation of the patient and of models Cranial x-ray LL, AP, dental panoramic x-ray Occlusal analysis of parafunctions: Brux Checker CPM and CPV analysis of the mandibular position Patient’s interview: first diagnosis Clinical and instrumental analysis 2 Gnathologic chart Recording of mandibular movements with electronic condylography (Cadiax® system) Condylograph’s components Para-occlusal clutch Registration of the articular dynamics Evaluation of condylographic tracings Final evaluation, diagnosis and treatment plan Diagnosis Treatment plan CHAPTER 3
Facial macro-aesthetics related to the mandibular position Introduction Cybernetic system Dental and facial aesthetic canons Aesthetics and underlying structure
Skeletal classifications Cadias® tracing on the LL Cephalometric points on the LL tracing Skeletal points Dental points Cutaneous points Cephalometric plans and lines Tracing on the anterior-posterior Cephalometric analysis Vertical analysis Sagittal analysis’ skeletal class Dental analysis: incisors Dynamic analysis: disclusion angle Aesthetics and incisors’ functions Upper incisors Lower incisors Vertical dimension and incisors CHAPTER 4
Occlusal plane Introduction Occlusal plane and craniofacial development Normal growth Development of a class II Development of a class III Development of a mandibular lateral deviation Posterior discrepancy concept according to Sato Third molars’ germectomy Occlusal plans Correlation between OP and TMJ Compensation mechanisms CHAPTER 5
Occlusal concepts Introduction Dentition development Postnatal period Milk teeth development period Full milk dentition period First stage of mixed dentition Second stage of mixed dentition Permanent mature dentition period Functional arches and structure of dental arches Functional areas of dental arches
Vertical dimension project according to the Vienna School Introduction Digital functional smile design (DFSD) Three-dimensional management of the vertical dimension VD variation in rotation and in rotational translation Dental and skeletal class variation and variation of incisors and OP inclination Gnathologically-guide dimplantology concepts CHAPTER 7
Occlusal Mandibular Repositioning Technique OMRT (Bassetti) Introduction Reference Position (RP) and Therapeutic Reference Position (TRP) concepts Functional space and vertical dimension Occlusal plane and vertical dimension’s management in mandibular repositioning Upper and lower first premolar’s role in mandibular repositioning Splint for occlusal mandibular repositioning Therapeutic provisional CPV use in reassembling technique From the therapeutic provisional to cases’ finalization Rehabilitative orthognathodontics with MEAW technique (Sato) Early Mandibular Repositioning Technique (EMRT) CHAPTER 8
The ten key points of the treatment plan Introduction 1. Removing the posterior discrepancy 2. Controlling the vertical dimension 3. Creating posterior support 4. Correlation between OP inclination and SCI 5. Sequential occlusion (Classes I, II, III and cross-bite) 6. Correlation between incisors and SCI, incisors’ control 7. Correlation between canine and SCI, laterotrusive and protrusive control 8. Correlation among molars, premolars and SCI 9. Retrusive control of the upper first molar 10. Retrusive control, protrusive guidance and protrusive control of the upper and lower first premolars
Clinical Case Studies Case Report 1 Case Report 2 Case Report 3 Bibliography
Acronyms APDI = antero posterior dysplasia indicator AXIO = axio-orbital plan C = milk canine, or the third tooth of the milk dentition CI = cusps inclination CNS = central nervous system CPM = condylar position measurement CPV = condylar position variator CCMD = cranial-cervical-mandibular disorder DA = disclusion angle DFD = digital functional design DFSD = digital functional smile design DRP = deranged reference position E = milk little molar, which is the fifth tooth of the milk dentition EMRT = early mandibular reposition technique FPS = functional prosthetic space ICP = inter cusp position (maximum intercuspation) LFH = lower facial height MEAW = multiloop edgewise arch wire MI = maximum intercuspation ML = mediotrusion left (mediotrusion left which is equal to the right laterality) MLD = mandibular lateral deviation MP = mandibular plane MPI = mandibular position indicator MR = mediotrusion right (mediotrusion right which is equal to the left laterality) NMS = neuro-muscular system OB = over-bite ODI = open bite dysplasia indicator OJ = over-jet OMRT = occlusal mandibular reposition technique OR = sub-orbital point that indicates the forward point of the axis-orbital plane OP = occlusal plane RCI = relative condylar inclination RCP = retral contact point RP = reference position
SCI = sagittal condylar inclination TMJ = temporo-mandibular joint TRP = therapeutic reference position VD = vertical dimension VTO = visual treatment objective
Transversality of gnathologic principles Introduction Gnathology should not be considered as a dental branch in its own right, but rather as a crossdiscipline touching every sector the attention of the clinician can be oriented to. The concepts underpinning new gnathology, defined by Professor Slavicek, allow following a unique operating strategy, used in all the rehabilitative branches of dentistry, from removable to fixed prosthesis, from implant prosthesis to orthodontics, both the one carried out during the developmental age and that occurring in adulthood. In the slow and gradual human evolutionary process, the masticatory organ has evolved as a multifunctional structural unit that today plays a role of central importance in the hierarchical system of the human body (Figs. 1.1-1.4).
Fig. 1.1 Evolution: evolutionary postural changes of man skull due to the transition to the upright position. (Modified from: Sato S., Master Course Donau Universität Krems)
Fig. 1.2 Developmental characteristics of primates’ skull: 1. large corner of the skull base (extension); 2. high posterior vertical dimension (yellow arrow); 3. upper maxillary bone with growth in forward and down direction (green arrow); 4. flat occlusal plane. (Modified by: Sato S., Master Course Donau Universität Krems)
Fig. 1.3 Developmental characteristics of the human skull: 1. less wide corner of the skull base (flexion); 2. lower posterior vertical dimension (yellow arrow); 3. maxilla with downward directed growth (green arrow); 4. steep occlusal plane. (Modified by: Sato S., Master Course Donau Universität Krems)
Fig. 1.4 Mechanisms that maintain the primate mandible forward and that are no longer present in humans: 1. canine stop (green); 2. posterior bone support given by the post glenoideus bone spine (red); 3. intercuspation in class I (blue); 4. high posterior vertical dimension (yellow) and flat occlusal plane. (Modified by: Sato S., Master Course Donau Universität Krems)
According to the cybernetic scheme conceived by Professor Slavicek (see Chap. 3, Figs. 3.1-3.2), the masticatory organ is an integral part of the human body and consists of the following structures: the neuro-muscular system (NMS), the temporomandibular joint (TMJ) and the occlusion. It is clear that we face an organ capable of performing different functions: the mastication, the speech, the breathing, the swallowing, the posture, the aesthetics and stress control (bruxism, clenching). Considering the mouth in this more dynamic way, it will be necessary to supplement or even to overcome the old gnathologic dogmas, introducing the principles of new gnathology, which are flexible and adaptable by definition, following a constant and controlled evolution.
Thinking gnathologically If it is true that the scientific evidence does not allow correlating dysfunction and occlusion, this relationship may be highlighted by clinical practice, when it is based on the evaluation of a significant number of cases. When the dentist has to make occlusal therapy, ranging from a simple filling of class 1 to complex rehabilitation, it will always be convenient to keep in mind the gnathologic principles. The same principles can correct and improve occlusal aspects, which, if not treated, would cause inevitable functional problems. Thanks to the gnathologic thinking, the clinical diagnosis will be complete, the treatment plan will take into account the signs and symptoms of dysfunction, having as a positive effect that of reducing the therapeutic risk. As an example, the most widely used classification of the occlusion is Angle’s one, but this only expresses a dental relationship without taking into account the functional skeletal
parameters, nor the mandibular position with respect to the maxillary bone and compared to the TMJ (Fig. 1.5). We should think that the teeth, and thus their relationship of intercuspation, affect the three-dimensional position of the jaw with respect to the upper arch, and that this position determines in turn a precise articular relationship (Figs. 1.6-1.7). Fig. 1.5 Patient assessment by dental and skeletal point of view.
Fig. 1.5A Right intraoral view of a class II dental relationship in a case of severe deep bite.
Fig. 1.5B Class I skeletal relations (with vertical dimension in the norm) highlighted by cephalometric tracing performed on the skull lateral.
Fig. 1.6 Same patient as in Fig. 1.5A and 1.5B: visualization of the change of the dental class relationship (toward I class) in the case of mandibular advancement towards the therapeutic position (TRP). Fig. 1.7 Evidence of the variation of the condylar position between maximum intercuspation (ICP) and therapeutic position (TRP), spatially evaluable in the three axes of the space X-Y-Z on the Condylar Position Variator (CPV), (with reference to Fig. 1.16).
Fig. 1.7A Change in the right condylar position on the X-Z axes.
Fig. 1.7B Change in the left condylar position on the X-Z axes.
Patient classification for a standard diagnosis Given the fact that gnathology is the keystone of a complete diagnosis and of a successful
therapeutic plan that will result in a significant reduction of risk, it will be helpful to frame the patient in one of the following three target groups: 1. Asymptomatic patient Patient with muscular problems without TMJ problems Patient with TMJ symptoms without pain 2. Patient with TMJ problems and pain Patient with severe occlusal and periodontal problems Patient with malocclusion and dysgnathia 3. Full prosthetic patient Implant-prosthetic patient Patient with cranial-cervical-mandibular disorders (CCMD), with dominance of psychological problems The inclusion of the patient in a group rather than another will be carried out according to symptoms. This initial classification in reference classes will allow the clinician to be more confident because he will be able to take into account any sign of dysfunction, which should always be searched for before beginning with a rehabilitation case. Therefore, the clinical intraoral examination supported by the observation of the models mounted on the articulator and by the panoramic dental x-ray, by the teleradiography and by the pictures (see Chap. 2), will highlight signs of crucial importance for a diagnosis that takes into account the functional aspects.
Therapeutic risks’ reduction and control Necessarily, a treatment plan is built considering the relationship between the following indicators: • the economic factor; • the level of patient cooperation; • the time that the patient decides to devote to the treatment path; • clinical and laboratory’s knowledge and skills; • control of therapeutic and laboratory phases; • communication between the dental practice and the dental laboratory. The respect and integration of all these factors allow obtaining a reduction and control of risks related to therapy, achieving the rehabilitation’s long-term stability. However, what has to be emphasized is that the gnathologic approach and the initial functional analysis phase will satisfy the respect of equilibria that have to be reconciled or maintained, as well as the patient’s aesthetic needs. It happens in some cases that the choice of treatment given by the clinician is affected either by the patient’s economic condition, or by his/her age, or by the specific request not to perform invasive and complex therapies. This is just to say that also the choice of a removable prosthesis rather than a complex rehabilitation on implants, must be managed according to functional canons, capable of satisfying the patient’s aesthetic needs. The economic aspect can influence the type of prosthetic therapy, but not the possibility to return back the function and an appropriate relational life to the patient.
Main patient requests Looking at the side of patients’ main requests, we can undoubtedly say that they concern aesthetics, long-term stability of the implemented therapies, and risks, treatment’s duration and costs reduction. Given the high percentage of TMJ problems, patients also ask for functional recovery, but not always as a priority. It must be said that they mostly tend to underestimate the dysfunctional aspect, especially when it does not directly relate to the dental apparatus; it is difficult for them to see any relationship among, for example, cervical problems, tinnitus, postural disorders or headaches and their occlusion type. Therefore, it will be a clinician’s duty, after a careful diagnosis, informing the patient about the gnathologic approach, inserting the mouth in a broader study context.
Looking for signs and symptoms of cranial-cervical-mandibular disorders (CCMD) On the basis of what said above, from the clinical point of view it will be necessary to be reckoned with any of the aspects listed, so as to obtain a diagnosis in line with the patient’s expectations. During the anamnestic process, the patient usually refers a symptomatology or a series of very specific symptoms, which, depending on the subjective pain threshold, can be more or less relevant for him/her. The symptoms usually characterizing the dysfunctional framework are: • headache; • neck and shoulders’ pain; • chewing difficulties; • feeling of incorrect dental fit; • articular problems (clicks, various types of pain); • bruxism; • tinnitus. The subjective perception of pain may be misleading, that is to say, lead to an erroneous assessment of the level of dysfunction if the clinician does not conduct a careful research of signs of dysfunction. Only if conducted in a thorough and complete manner, the diagnosis will be also useful to minimize therapeutic risks. The recognition and subsequent consideration of particular signs will determine the need for a diagnostic in-depth study, which will result in a specific diagnosis and treatment plan (Fig. 1.8). A careful compilation of the gnathologic chart will allow on the one hand all the symptomatology to be defined before starting the therapeutic path, on the other hand the evolution during the treatment and at the end of the therapy to be controlled.
Fig. 1.8 The ortho-panoramic x-ray highlights a significant demodelling caused by functional overload of the surface of the right and left condyles.
Sometimes it can happen that during the treatment the patient can report a symptom that had already been diagnosed as a sign, and therefore not attributable to the work of the clinician who had already informed the patient about its appearance. For example, an articulation exposed for years to a chronic block, so that the patient is accustomed to it, can determine an almost regular opening of the mouth, even if mostly obtained by rotation movements and with minimal or no translation. It can be the case that during the therapy a click may reappear, which the patient reports as a problem and not as the initial phase of an articulation unblocking. This will not constitute a problem if in the initial case history interview questions have been provided, aimed at highlighting symptoms that patients often tend to minimize. To the question: “Have you ever heard joint noises?”, the patient will respond positively referring the symptom to long time ago. He/she might add that the symptoms are then disappeared, he/she shifted to a stage where he/she could not open his mouth well and then, over time, in his/her view everything went back to complete normality. In this case the patient has to be informed about the presence of a chronic block, to ascertain with adequate diagnostic procedures and that the clinician will try to unlock during the therapy. Thus, the recurrence of joint noises could be considered as a positive sign and not as a pejorative. This exemplification in order to emphasize that for the success of a more or less complex dental therapy, we have to keep in mind the information inferred from the medical history and the symptoms reported by the patient and, above all, the signs indicating the dysfunction (Fig. 1.9). If the dentist is going to run a rehabilitation treatment, certainly he can not underestimate the symptoms reported by the patient, including those related to non-oral districts and investing the expertise of other specialists, in the view of an interdisciplinary resolution of the problem. Fig. 1.9 Signs of dysfunction.
Fig. 1.9A Interdigitations of the arches’ shape on the lateral edge of the tongue in a clenching patient. To note, the loss of the anatomy of the incisal edge of the lower incisors.
Fig. 1.9B The lesions of the lower incisors are mirroring those of the upper incisors. These dysfunctional signs should be carefully evaluated before proceeding with an aesthetic restoration.
Some symptoms, such as headaches, pain in the neck (cervical pain), chewing difficulties, problems related to the TMJ, bruxism, clenching, are closely related to dental problems and not to take them into account could expose the clinician to significant risks of therapeutic failure. The clinician has to be sharp in the search for signs of dysfunction, using the diagnostic procedure that will be explained below. When these signs are known to the clinician, they will be found in the majority of patients in a more or less accentuated way (Fig. 1.10).
Fig. 1.10 Dental element 28 hyper-extruded creates interferences during functional movements.
A careful intraoral examination of the arches and of the plaster models are able to highlight signs of dysfunction such as: • late rotrusive, mediotrusive and protrusive wear facets; • recessions of the gingival tissue and injuries to the cervical part of the tooth not due to tooth decay; • mobility and sensitivity of the teeth; • flaring of the upper incisors with diastemas’ opening; • severe dental wear with loss of dental anatomy; • wisdom tooth that creates functional interferences; • inter digitations of dental arches’ shape on the lateral side of the tongue (Figs. 1.9-1.14). Fig. 1.11 Periodontal Problems related to dysfunction.
Fig. 1.11A Gingival recession of 14-13 with adjoining collar injury with parafunctional etiology.
Fig. 1.11B The brux checker highlights the cause of the problem, namely the night parafunction borne by the 14-13. Fig. 1.12 Dysfunctional signs in a case of Class II with deep bite.
Fig. 1.12A Patient with severe collapse of the vertical dimension.
Fig. 1.12B Inferior crowding due to the deep bite and wear facets on the vestibular surface of the lower incisors,
caused by the parafunction. This parafunction was caused by a too retruded mandible, which tries to gain space anteriorly. Another sign of the need for anterior space is the opening of the diastema between 11 and 12. To note, the significant segment elevation of the gingival parabolas between canines and lower incisors. Over the years the parafunction will completely destroy the lower incisors. The process is certainly not justifiable through the concept of abrasion and extrusion; it depends only on the anterior bite closure associated with parafunction. The segment elevation of gingival parabolas was already present and constitutes a peculiar characteristic of this type of malocclusion.
Fig. 1.13 The lateral of the skull of the above patient, shows a high-angle skeletal class II; this aspect would not be detectable to the clinical examination which, indeed, could lead to an erroneous diagnosis. Fig. 1.14 Signs of dysfunction on study models.
Fig. 1.14A Wear facets on the plaster cast of the lower arch; these contacts are not detectable in the mouth with articulating papers, because of the strong canine dominance due to the deep bite.
Fig. 1.14B The brux checker highlights the night parafunction.
Today, many young patients show serious problems related to loss of tooth substance. This deficiency is often attributed solely to chemical agents. For the purpose of a comprehensive diagnosis, it is the case to consider the incidence of causes related to parafunction and malocclusion, to the benefit of a good therapeutic outcome. Let’s consider the case of a patient with severe wear of the posterior molar-premolar sector whose primary cause lies in parafunction; this reveals a problem of clenching and transverse bruxism, due to the front wall created by the deep bite. This case requires a therapeutic intervention that goes beyond the creation of a minimum of space for the thickness of restorative materials, as it is clarified by the images below (Figs. 1.15-1.17). Normally, in the view of a minimally invasive procedure, the availability of about 0.8 mm per arch is required to reconstruct the occlusal surfaces in lithium di-silicate. However, the only reconstruction carried out by opening the space in rotation (scissor opening), without providing a functional diagnosis of the problem, would orient the clinician towards a wrong therapy from the functional point of view. In effect, following this path to increase the vertical dimension (VD), the clinician would get little posterior space and an anterior open bite whose necessity to close would force in a much more invasive treatment (orthodontic or prosthetic), recreating the dysfunctional problem (Fig. 1.18). The solution of the problems in question lies instead in the three-dimensional repositioning of the mandible through the Occlusal Mandibular Reposition Technique, OMRT (Bassetti), (see Chap. 7). It allows, through the anterior translation movement to which must be associated a counterclockwise rotation, obtaining posterior space without a counterproductive opening of the anterior bite (Fig. 1.19). Fig. 1.15 Erosion of the posterior sectors of the dental arch caused by parafunction, which is associated with a multifactorial mechanism (food-beverage-toothbrush).
Fig. 1.15A Upper arch.
Fig. 1.15B Lower arch. Fig. 1.16 From ICP to TRP.
Fig. 1.16A Right lateral view in ICP.
Fig. 1.16B RP position showing the therapeutic position. You may notice the space created in the back without an anterior opening of the bite and the improvement of the relationship of dental class I due to the mandibular advancement.
Fig. 1.17 Upper arch after reconstruction made in composite with minimally invasive direct technique. It was then suggested a night protective mask, vacuum-formed and very thin.
Fig. 1.18 Effect of the increase of the vertical dimension with scissor opening, clockwise rotation and downward and backward mandibular shift. In this case we get a wedge-shaped space with posterior apex and risks of an articular overload especially in high-angle II classes.
Fig. 1.19 Effect of the increase of the vertical dimension with counterclockwise rotation and forward and downward movement of the mandible along the inclination of the palatal surface of the upper incisors. In this way the interocclusal space is almost identical across the posterior sector, with the further advantage of unloading the articulation.
Therefore, in contrast to the VD variation with scissor opening, we will obtain the necessary space in the posterior sector in a functionally adequate mandibular position through a threedimensional repositioning of the mandible. In this way, the lower incisor will slide along the S1-S2 way (see Chap. 3) placing itself in a lower and more advanced area. At this point, the position will be blocked thanks to a resin gig and the posterior sectors will be reconstructed through a direct technique, if the clinician is capable of mastering the procedure. To obtain a higher degree of precision and safety, for the reconstruction we will make use of silicone masks resulting from a functional wax-up in Therapeutic Reference Position (TRP) carried out on models mounted on articulator. This option, certainly more predictable, produces though an increase in treatment costs, as well as in execution time. For the clinician the pre-contact feeling reported by the patient
should not be cause for alarmism; this will disappear almost immediately due to the counterclockwise rotation of the mandible obtained thanks to the increase of posterior support. The images testify an elementary direct approach to achieve once the right diagnostic concepts are met (Fig. 1.20). Fig. 1.20 Opening of 4 mm with scissor effect: the result is little posterior space and an anterior open bite.
Fig. 1.20A ICP Position.
Fig. 1.20B Opening only in rotation: view of the obtained interarch space. The retrusion of the mandible that follows worsens the Class II relationship.
Fig. 1.20C Evaluation of the opening of the posterior space after the mandibular repositioning in rotation and anterior translation; to notice: the opening of an uniform space in the posterior area, the correction of the dental class, the absence of anterior bite’s opening.
The following images refer to a bruxer with deep bite; the parafunction hit the incisors’
sector, leaving undamaged the posterior region. This occurred because the mandible could create a functional space forward, eliminating the deep bite and preventing articular problems. These outcomes are not explainable using the wear-extrusion theory of the lower incisors’ group, but are classic situations of deep bite with interincisal high-angle on skeletal types tending to class III, deep bite, where the anterior jump of the bite did not occur. Once again, the patient’s skeletal classification is crucial for framing a correct therapeutic plan (Fig. 1.21). Fig. 1.21 Deep bite case with evident destruction of dental tissue in the incisor sector.
Fig. 1.21A Frontal vision in edge-to-edge position, which highlights the significant destruction of dental tissue and the remarkable openness of the posterior space due to the deep bite.
Fig. 1.21B Detail of dental substance destruction in the palatal area of the upper incisors. How to intervene?
Without taking into account the functional aspect, since the therapeutic goal is the reconstruction of the incisor group, a possible intervention could consist in the opening of the vertical dimension, then using the periodontal surgery to lengthen the clinical crown of the
lower incisors, so as to limit the opening of the posterior space. But this approach would prevent the mandible to move forward and would recreate a front wall with serious dysfunctional problems and high risk of treatment failure. Since the cause of the problem is a too retruded mandible and too right teeth, it is necessary to move towards the three-dimensional repositioning of the mandible with a forward movement and clockwise rotation, in order to have enough anterior space without excesses of space in the posterior sector. Still it is appropriate to create posterior support with minimally invasive prostheses, to change the inclination of the palatal surface of the upper incisors (correlating this surface with Sagittal Condylar Inclination) by means of an orthodontic and prosthetic treatment (Fig. 1.22). Fig. 1.22 Therapeutic position of the case in Fig. 1.21.
Fig. 1.22A New functional space after mandibular repositioning.
Fig. 1.22B Masks of the duplicate of sequential wax-up according to Slavicek.
Fig. 1.22C Prototype of the rehabilitation for the functional and aesthetic evaluation.
When for therapeutic purposes the VD has to vary, it will not suffice to consider the concept of rotation and to obtain enough space for the restorative materials; also the fact that the mandible can, indeed must, reposition itself in three dimensions will in fact deserve its right consideration. This will force the clinician to interface with the new concepts of Reference Position (RP) and of TRP, and thus considering the three-dimensional change of the mandibular position. That is why any rehabilitation project first of all has to provide for a phase needed to establish the mandibular position (TRP), secondly the dental or implant position (gnathologically guided implantology), thirdly the dental class relationship and finally the aesthetic result. Conversely, if the dental relationship were established first, the clinician could not be sure that the resulting proportions between the upper and the lower jaw are functional and in harmony with the TMJ and the muscles. When it comes to full dentures, the vertical dimension is the first thing that has to be set, followed by the consequent mandibular position in relation to the TMJ. After that only, it will be possible to perform the mounting of the teeth according to individual functional parameters, with static and (especially) dynamic aspects that will lead to an adequate aesthetic result. When the parafunction has not created damages the tooth’s occlusal surface, an orthodontic philosophy like the MEAW one, which is based on the control of the occlusal plane (OP) and of the VD and allows the mandibular repositioning, becomes a curative treatment and a prevention tool from the functional point of view (Fig. 1.23). Fig. 1.23 Deep bite case with evident aesthetic impairment in which the adaptation of the organism through lower crowding allowed a forward positioning of the mandible avoiding articular problems. Case solved without extractions, with orthodontic treatment according to the MEAW-SATO philosophy.
Fig. 1.23A Pre-treatment frontal view.
Fig. 1.23B Face macro-aesthetics, post-treatment.
Fig. 1.23C Frontal view of the occlusion in ICP, after a proper management of the OP and of the VD.
Analog and digital gnathologic diagnostic flow Introduction According to the most recent international studies, supported by statistical data, a percentage of the population from 15% to 40% suffer from more or less serious dysfunctional problems borne by the temporomandibular joint (TMJ); the percentage increases if we consider patients who require complex oral rehabilitation. The therapeutic planning for these patients requires a precise diagnosis, to avoid erroneous treatment plans, with often unsatisfactory results from the aesthetic, functional and economic point of view. As in any other branch of medicine, also in dentistry the diagnostic part reckons, in addition to the clinical stage, on a series of instrumental examinations. Following diagnostic schemes divided in well identified phases - which will be explained to the patient by means of digital and paper supports during the first visit’s interview - the goal of letting the patient feel that the treatment plan is always the result of a reasoned study, will be achieved. The patient will perceive his/her own treatment plan as never comparable to that of another patient and never reducible to minimum, since aimed to pursue the therapeutic success, eliminating the risk factor and also avoiding wrong diagnoses and/or treatment plans. Therefore, after the initial visit, a brief medical history will be carried out, the clinician will evaluate the patient’s requests, calling for a “guaranteed” solution of the problem, and he/she will give explanations about the gnathologic diagnostic process he/she is about to follow. These moments can be summarized as follows: • visit; • short medical history; • patient’s requests and expectations; • explanation of the gnathologic diagnostic procedure. The gnathologic diagnostic phase, the last one among those cited above, will develop into: a) clinical and instrumental analysis 1, which allows making a preliminary diagnostic evaluation on the basis of collected data and it is useful to explain to the patient the pathologies which he/she is suffering from; b) clinical and instrumental analysis 2, which will go more indepth, allowing finalizing the diagnosis and undertaking the subsequent, definitive treatment plan.
Clinical and Instrumental Analysis 1 The clinical and instrumental Analysis 1 includes a general and a dental, gnathologic medical
history: this will be the right moment for determining the possible link between the existing problem and its dysfunctional cause. The dental visit will be thus oriented towards a gnathologic approach with a targeted palpation of the masticatory muscles (TMJ) and an evaluation of the mandibular dynamics, as well as towards the identification of the unequivocal signs of dysfunction described in Chap. 1. In this way, with a wide range of anamnestic elements available, it is possible to recognize the cause of the problem and to show it to the patient, with the help of digital and paper supports. The next steps of the diagnostic flow will be indicated to the patient in order to start with a suitable initial treatment. In emergency cases, i.e. when patients show acute dysfunctional problems (e.g. articular locking with sharp pain), the clinician should immediately implement therapies such as the emergency splint, or drug-therapies in order to relief the acute pain; in this case the diagnostic phase will be necessarily delayed (Fig. 2.1). Concluding, the initial diagnostic phase, if systematically carried out, ensures the possibility of a specific clinical intervention and gives the chance of recognizing through the symptoms also other kind of health issues, not directly related to the teeth. Fig. 2.1 Patient suffering from acute articular locking.
Fig. 2.1A Patient with acute left articular locking: note the reduced opening (24 mm) and the mandibular deviation when opening towards the side of the locking.
Fig. 2.1B Emergency splint to reduce the pain and induce the left joint unlocking; in this context there is no contact to the right side to let the mandible tilting on the same side.
From the impression to the diagnostic model The basis of the diagnostic investigation are the dental arches of the patient: panoramic and precise plaster models of both the two arches to be mounted in the articulator are then necessary. It must be said that all the diagnostic model management should preferably be performed in the dental practice. This phase, which is often underestimated, is a critical step for diagnosis: in fact, if incorrectly or too superficially done, the diagnosis can be wrong. The impression will be taken in alginate with closed tray, or with slotted tray, prepared ad hoc. If the impression was poured in a laboratory instead of the dental practice, it would be better to use silicon-based materials, which do not require an immediate pouring and allow getting more than just one model from the same impression. The impression has to be panoramic, including arches, trigoni, tuberosities and all the teeth, the impression’s material must also have uniform thickness, without teeth’s contact on the tray. It will therefore be necessary to adequately prepare the tray, creating with the wax some stop zones: a palatal one for the superior tray and three vestibular stop areas for the inferior tray (one in the front and two lateral-posterior, in the buccal shelf area). In some cases, a fourth stop will be created in the central lingual zone, on the inferior tray (Figs. 2.2B-2.3). The squaring of the model must be carried out respecting the squaring canons of orthodontic models, safeguarding the arches and keeping the panoramic aspect detected with the imprint. Fig.2.2 Preparation of the impression trays from which is detectable the stop wax position.
Fig. 2.2A Preparation of the upper tray.
Fig. 2.2B Preparation of the lower tray.
Fig. 2.3 Selection and preparation of the standard slotted tray; the position of the stop in wax is always the same.
W ith the packing tape the upper holes and several lateral holes are closed, leaving opened the other lateral holes for the retaining of the impression material.
Fig. 2.4 Between teeth and tray is evident an uniform space for the impression material, created by the stop in wax.
Fig. 2.5 Material needed for the detection of the alginate panoramic impression. Fig. 2.6 Impression extension, possible contacts of the teeth on the wax are not harmful if the impression is immediately poured.
Fig. 2.6A Upper impression’s extension.
Fig. 2.6B Lower impression’s extension. Fig. 2.7 Model’s development phases in the dental practice.
Fig. 2.7A Material needed to manage in the dental practice the model’s development.
Fig. 2.7B Plaster’s pouring with the help of the vibrator.
Fig. 2.8 Upper model before squaring: note the excess amount of plaster required for a correct squaring.
Starting from the upper model, the base will be squared, parallel to the occlusal plane. Then the posterior part will be squared as well, perpendicular to the midline of the model, sketching the other seven sides respecting defined angles. The same thing will be done on the lower model, leaving a margin of adjustment for the last finishing with the upper model; thus the assembly will be done in maximum intercuspation (inter cusp position, ICP). After the mounting in the articulator, the symmetry obtained by the squaring could be lost; in this way further and important information for the diagnosis will be obtained (Fig. 2.9). An error in the squaring, however, could lead to an asymmetrical model, maybe inducing to consider the maxilla rotated, ending up with anerroneous diagnostic evaluation, both as regards the prosthesis and the orthodontics. Fig. 2.9 Squaring of the upper and lower models according to orthodontic canons.
Fig. 2.9A Squaring of the basis of the upper model, parallel to the superior occlusal plane.
Fig. 2.9B Shaping of the upper model’s posterior part, perpendicular to the midline.
Fig. 2.9C Squaring of the seven sides of the upper model.
Fig. 2.9D Squared models (ICP) ready for the mounting on the articulator.
Therefore it is the case to emphasize the extreme importance of the “squaring”; in this regard, observe figures 2.10A and B. In this phase, upper and lower models will be just classical models, without provision for split cast, so that they will result easily manageable in the dental practice. Fig. 2.10 Asymmetries due to erroneous model’s squaring.
Fig. 2.10A Upper model with the posterior part not perpendicular to the midline: this may erroneously lead to think of a rotation of the maxillary bone to the left.
Fig. 2.10B Restoring the perpendicularity of the model’s posterior wall to the midline avoids the error shown in Figure 2.10A. N.B: In both figures the red mounting plate is the reference point in the transversal and in the sagittal direction, detected on the patient by means of the face bow.
After having carried out the development and the squaring, three pins will be applied to the lower template. As an alternative to this technique, a magnetic split cast can be built both on the upper and on the lower model, after the squaring. The advantage of these two building methods of the lower model will be that of allowing more mountings in the articulator of the same model but in different positions, all comparable among them (Figs. 2.11 to 2.13).
Fig. 2.11 Lower model components with 3 pins, after the mounting on articulator.
Fig. 2.12 Lower model and mounting plates in different ICP and RP positions, useful for testing one or more therapeutic positions using the same model.
Fig. 2.13 Full dental’ case in which the same model (the lower) with magnetic split cast was mounted in five different therapeutic positions (replacement technique).
In special cases, for a precise and detailed assessment of the occlusion, it will be necessary to build the antagonist inferior pin model, as indicated by Slavicek, with the base equipped with split cast. This model has the characteristic of being able to individually separate each tooth while maintaining the lower incisor group in just one block. Of course, the same procedure will be implemented for the upper model, in case it should be necessary to work over the lower model (Fig. 2.14). If the Slavicek’s pin model is used in prostheses for the construction of sequential guides, it will be prepared by the dental technician, with Zeiser or affine technique (Figs. 2.15 to 2.16). Fig. 2.14 Pin model according to Slavicek.
Fig. 2.14A Lower pin model according to Slavicek.
Fig. 2.14B Evidence of the ability to pull out every single tooth and the incisal group in one block.
Fig. 2.15 Lower pin model, indispensable for building the sequential occlusion with canine dominance in the upper rehabilitation. The figure highlights a phase of the sequential occlusion: the first premolar discludes all the posterior sector in the left mediotrusive movement.
Fig. 2.16 Use of the lower pin model also in case of a single crown on the tooth #36; this technique allows excluding the functional dominance of the mesial teeth on the crown itself.
Face bow and mounting on articulator of the upper cast In order for the upper and lower model to be correlated with each other, both statically and dynamically, as it is on the patient, we will need an articulator with individual values. At this point, the face bow will allow transferring on the articulator the three-dimensional cranial position of the upper jaw according to precise references that are able to define a reference plane, called the axis-orbital plane. The axis-orbital plane will be chosen as the reference plane because of its replicability, individuality, identifiability on the patient as well as its traceability both on the articulator and on the cephalometric tracing. The axis-orbital plane is defined ahead by the left sub-orbital point OR (identified by palpation), and by two posterior points, right and left, of the individual hinge axis, localized through the electronic condilography.
On the articulator, the condyles represent the two hinge axis points, left and right, whilst the tip of the incisal pin positioned at zero represents the suborbital point (Fig. 2.17). Fig. 2.17 Axis-orbital plane.
Fig. 2.17A Axis-orbital plane (red line) and Frankfurt plane (green line) detected on the patient.
Fig. 2.17B Axis-orbital plane on the articulator.
Fig. 2.17C Lateral skull’s x-ray: the red line indicates the arbitrary axis-orbital plane, whilst the green line shows the Frankfurt plane.
The model of the upper jaw can be mounted on the articulator in two ways (Figs. 2.18 to 2.19): a) on arbitrary hinge axis, using an anatomical arch; b) on individual hinge axis, using a kinematic face bow. Fig. 2.18 Anatomic face bow.
Fig. 2.18A Anatomic face bow mounted on the patient.
Fig. 2.18B Mounting on articulator of the upper model in arbitrary hinge axis. Fig. 2.19 Kinematic face bow.
Fig. 2.19A Kinematic face bow after electronic individual hinge axis’ localization.
Fig. 2.19B Mounting on articulator of the upper model in individual hinge axis.
Statistically the arbitrary axis-orbital plan form a 5° angle with the Frankfurt (FR) bone plane: they share the same anterior left suborbital point OR. The Frankfurt plane is easily localizable on the cephalometric tracing of the side of the skull, as defined by two bone points, respectively Porion (Pr) posteriorly, and Orbital (OR) anteriorly. Starting from the anterior OR point, considering an angle of 5° downwards, the arbitrary axis-orbital plan can be identified, setting the hinge axis point at the point where this line intersects with the axis of the condyle. The anatomical arch is used in a simple and rapid way, and is also reliable because the two planes, the Frankfurt and the axis-orbital, are almost parallel. In the initial diagnostic phase, the mounting on the articulator will be performed with the anatomical face bow, reserving the individual face bow use to subsequent diagnostic and therapeutic-rehabilitative phases (Fig. 2.20). Fig. 2.20 Difference between mounting of the upper model with and without face bow.
Fig. 2.20A Mounting with face bow on the axis-orbital plane.
Fig. 2.20B Mounting without face bow, according to the patient Camper’s plane or to the patient occlusal plane. It is deducible that in dynamics the two systems will operate in a completely different way and also the inclination of the incisors will be completely different.
From the images it is possible to detect the difference of occlusal relationships and of the occlusal plane’s inclination, depending on the chosen reference. Even in orthodontics all patients’ models will be mounted on the articulator with an arbitrary arch. The only squaring of orthodontic models will not provide any useful indication from the diagnostic point of view on their actual spatial position, if subsequently they will not be mounted on the articulator (Fig. 2.21). Fig. 2.21 Mounting of models with and without face bow.
Fig. 2.21A Model with orthodontic squaring and horizontal occlusal plane.
Fig. 2.21B Variation of the occlusal plane inclination after mounting on articulator.
The arbitrary face bow has a remarkable versatility and can be also used for young patients, from 4-5 years of age onwards. Already at this stage, with the anatomic bow mounted on the patient, it will be important to detect any asymmetry of the frontal and horizontal planes, but they still do not entail the need to adopt the corrections on the facial arch, to parallelize it with respect to the horizontal and frontal planes. The bite fork is prepared by sticking three Bite-tabs, a frontal one in the central incisors’ area, and two posterior, respectively right and left, in the first molar area. In this way, three indentations arranged as a tripod are obtained on thermoplastic material. They guarantee the perfect stability of the model. Multiple indentations on other types of less precise materials, such as waxes or silicones, are not recommended. The Bite-tabs made in thermoplastic material constitute a stable base of connection between indentations and bite fork: then, they are relayed with further thermoplastic material with a lower softening temperature, before positioning the bite fork in the mouth to indent the contacts. This method avoids the excessive heating of the first thermoplastic material that serves as a support to the relaying material and also avoids the excessive sinking of the teeth in the material, as well as their possible contact with the metal of the bite fork (Fig. 2.22). The indentation of the three points is done inside the mouth and not on the plaster model, so as to avoid the risk of damaging the plaster teeth. Once the thermoplastic material will harden, the bite fork will be taken off and the excessive depth of indentation will be removed with the scalpel, reducing it to about 0.5 mm (Fig. 2.24).
Fig. 2.22 Preparation of the bite fork. The first thermoplastic materialis rebased with a second one that softens at a lower temperature.
Fig. 2.23 Indentation of Bite-tabs, performed directly in the mouth.
Fig. 2.24 Indented bite fork and finishing of indentations: worth noting, the tripod shape of the indented arch points.
Thus, the bite fork stability will be rechecked and the position registered with the kinematic or anatomic face bow. The anatomic face bow AB (Reference) does not need screwdrivers for locking the bite fork: having a joint that allows a great mobility without force and an equally secure clamping, it is easy to use and can be managed by the clinician alone (Fig. 2.25).
Fig. 2.25 Registration made with just two hands, after the face bow’s stabilization: a hand stabilizes the bite fork on the teeth while the other tightens the joint.
Then comes the phase of the assembly of the anatomic face bow, with the bite fork-joint, the support-arch and the support-bite fork kits for the mounting on the articulator (Fig. 2.18B). The same procedure can be used for full dentures, using as a support for the bite fork the resin plates for the assembly (Fig. 2.26). If the teeth concerned by contact are instead movable, it will be necessary to build the indentation not in the mouth, but on the plaster model in order to avoid intrusions or displacements of the dental elements. In case of missing teeth, the contact with the tripod will not always be achievable; then other contact points should be sought for, in order to obtain a stable position of the model on the bite fork.
Fig. 2.26 Bite fork for full dentures; detail of the plastering of the model’s split cast base to the distance block with
a minimum amount of plaster, in order to limit the distortion due to hardening of the plaster.
Fig. 2.27 The figure shows the perfect mating between the plaster teeth and the indentations performed in the mouth.
Fig. 2.28 Preparation of the bite fork in case of implants, using the provisional.
Particular attention will be required when deep indentations on the incisors will be carried on: in fact, opening the upper branch of the articulator, there exists a risk of fracturing the incisors’ edge. This drawback can however be avoided by decreasing the depth of indentations, and by loosening the locking of the joint on the arch, once the plaster hardened, before opening the branch of the articulator. In order to mount more upper models with the same face-bow registration, it will be pivotal not to unlock the joint, otherwise the recording position will be lost, together with the possibility to assemble other models in the same position. It is possible to mount more superior models in the same position by using the same registration. In this way, eventually the possibility to interface all the mountings made will be acquired. In practice, a master model should be always stored, while using one or two working models; in this way at every stage there will be the opportunity to recheck the work already done compared to the original situation. The arbitrary arch AB (Reference) will always provide the certainty of having placed the hinge axis within the circle which is located in
correspondence of the condyles of the articulator (Figs. 2.29 to 2.32). Now the mounting in the individual hinge-axis will be explained (Fig. 2.19). Fig. 2.29 Ratio between the anatomic face bow AB and the underlying structures.
Fig. 2.29A The posterior green circle indicates the ear plugs, the anterior green circle is placed in the condyle area with a diameter of roughly 1 cm, the anterior red dot indicates the OR bone point.
Fig. 2.29B Correspondence among the condylar housing of the Reference SL articulator, face bow and anatomical structures. • acoustic meatus (green circle), and ear plug; • condyle (anterior red circle), face bow circle (golden ring), condyle of the articulator.
Fig. 2.30 The perfect location of the anatomic bow AB on the reference points, with identification of the axis-orbital plane.
Fig. 2.31 Angled image with positioned face bow. From the distal position are identified: earplug, condyle area with hinge axis, OR anterior point. Hygienic covers on the earplugs (porus supports).
Fig. 2.32 To the left: physiological position of the head using as a reference the horizontal axis-orbital plane (green line); to the right, with reference to the Camper’s plane (blue line), it is highlighted the excessive counterclockwise rotation of the head, of the models and of the relative OP (red line).
This method allows the exact positioning of the upper model according to individual values. Attention should be given to the possible inclusion, on the frontal and horizontal planes, of angles due to the lack of symmetry between the right and left individual hinge axis points. If additional references for the correction of these plans are not provided to the technician, there is a risk that at the try-in the prosthetic device will be inclined, if viewed from the front (frontal plane), and rotated to the right or the left when viewed from above (horizontal plan),
resulting in evident problems for the aesthetics (Fig. 2.33). Fig. 2.33 Mounting in individual hinge axis.
Fig. 2.33A Asymmetry on the frontal plane (Z axis): in this case the maxillary model will be higher where the point of the hinge axis is lower.
Fig. 2.33B Asymmetry on the horizontal plane (X axis): in this case the maxillary model will be rotated towards the hinge axis point that is located more forward.
In order to obtain correction parameters, before dismantling the kinematic face bow from the assembly accessory, detected differences in level have to be measured, so that the technician can use these values to change the slope of the articulator through appropriate marks-up.
The same anomaly, with the same effects on the position of the model, can be seen with the anatomic face bow when the right and left acoustic meatus are asymmetric on the vertical and horizontal plans. In the event that the arch appears inclined on different planes, before fastening the joint with the help of the assistant, the face bow has to be parallelized again on the horizontal and on the frontal planes, so as to fix the relations according to this necessary correction (Figs. 2.34-2.36A).
Fig. 2.34 Asymmetry on the frontal plane, with the right acoustic meatus lower than the left one: to the left, without face bow’s correction, the incisors on the model are inclined; to the right, the effect of correction and the return of the incisors’ edge, horizontally. Fig. 2.35 Symmetry evaluation on the horizontal plane.
Fig. 2.35A Symmetry of the face bow on the horizontal plane seen from above (12 o’clock position).
Fig. 2.35B Asymmetry of the face bow in the horizontal plane seen from above (12 o’clock position): it is caused by a backward position of the left acoustic meatus; on the articulator the upper model will be turned to the right. Fig. 2.36 Asymmetry on the horizontal plane and effects on the upper model position on the articulator.
Fig. 2.36A Face bow asymmetry on the horizontal plane seen from the bottom (6 o’clock position), due to a backward right acoustic meatus with respect to the left one: the orange arrow indicates the direction in which the asymmetry correction has to be made before fastening the face bow joint for the registration. B-C On the
articulator the lower and upper models will be rotated to the left, thus leading to an incorrect assessment of the midline as well as of the aesthetic parameters.
In the sagittal direction, it will be better to rotate the anatomic face bow only after entering the earplugs (porus supports) in the acoustic meatus, so that the anterior part of the anatomic arch coincides with the suborbital point (Figs. 2.18A-2.31) before fastening the joint. This possible correction avoids model’s inclinations on the sagittal plane and, consequently, erroneous evaluations of the OP inclination and of the incisors’ axis. To sum it up, the upper model may be subject to: • rotations on the horizontal plane, towards the side where the hinge axis point, whether it is arbitrary or individual, is most advanced; • inclinations upwards on the frontal plane, on the side where the hinge axis point is located lower on the frontal plane; • inclinations in the anterior-posterior direction on the sagittal plane. The foregoing shows the need to have an anatomic face bow with high versatility in order to be able to implement the corrections and to make the mounting on articulator reliable, respecting a precise spatial position of the models. The steps shown in Figure 2.37 are those following the registration of the upper jaw position, i.e. its transfer onto the articulator (Figs. 2.37 to 2.38). Fig. 2.37 Plastering procedure of the upper and lower model.
Fig. 2.37A Face bow positioning on the articulator with the assembly aids (support for the bow and support for bite fork).
Fig. 2.37B Choice of the distance block, positioning of the plaster for articulators.
Fig. 2.37C Choice of the distance block, positioning of the plaster for articulators and closing of the upper branch.
Fig. 2.37D Articulator’s rotation, choice of the distance block and plastering of the lower model in ICP.
Fig. 2.37E Positioning of the plaster for articulators on the model and on the distance block.
Fig. 2.37F Closing of the articulator’s lower branch.
Fig. 2.37G Mounting of models in ICP completed.
Fig. 2.38 Overlay of the articulator to the face, according to the axis-orbital plane (red).
Fig. 2.38A Upper branch overlapping the patient’s face.
Fig. 2.38B Lower branch overlapping the patient’s face.
Reference wax and mounting on articulator of the lower cast Once the upper model has been mounted, its relationship with the lower antagonist has still to be determined. To this end, two ratios will be taken into consideration: 1. the maximum intercuspation ratio (ICP), looking for the mating key, without interposing
materials such as waxes or silicones (this detection has to be made by the clinician, since, in cases of doubt, he will have a chance to recheck the relationships directly into the patient’s mouth); 2. a relationship, released from teeth, called reference position (RP), recorded in the mouth, on a wax basis. If on the one hand the mounting in ICP is easy to do and does not require special expedients, we must instead explain more carefully the mounting of models in reference position, by following the procedure outlined below. First, the material to be used in this phase will be the Beauty Pink X-Hard wax, in double sheet; for its adequate handling and use, a thermostatic pot is indispensable. It will be preferable to build three waxes in order to record three positions and to be able of comparing them among each other: the triangular shape of the wax sheet will completely cover the upper arch up to the buccal cusps in the molar, premolar and canine areas. It is not recommended to execute this adaptation inside the patient’s mouth, since the result would be highly inaccurate and not usable (therefore this step must be rigorously carried out on the plaster model). It is preferable to construct the registration wax of the RP in the dental practice but this task may also be delegated to the laboratory. The direct management of several operating steps in the dental practice will reduce not only time and costs but also will allow to conduct a precise analysis and control of the therapeutic procedures. On the one hand the incidence of errors can be reduced, on the other further stressful sessions of devices’ remaking and adaptation can be avoided (Figs. 2.39 to 2.40). The anterior apex of the wax triangle will be found beyond the incisors, in order to avoid the upper lip falling over the upper incisors and obstructing the view during registration (Fig. 2.41). Fig. 2.39 Building phases of the RP wax.
Fig. 2.39A Required material for building the wax sheet for RP.
Fig. 2.39B Bending of the wax sheet in order to doubling its thickness.
Fig. 2.39C Adaptation of the wax sheet to the model.
Fig. 2.39D Cutting of the sheet carried along the indentation of the buccal cusps.
Fig. 2.40 Sheet adapted to the superior model; perfect adaptation of the sheet to the model and definition of the wax edge along the upper buccal cusps.
Fig. 2.41 The fingers (left forefinger and left thumb) take the wax; its triangular shape eliminates the visual interference of the upper lip allowing controlling the indentation of the lower incisors on the wax. Thumb and forefinger of the right hand leaning the chin; be careful not to exert forces that would lead to an erroneous registration.
The wax plaque must perfectly mate with the occlusal surfaces of the upper teeth and must not oscillate. All these features must be verified in the mouth before registration. If the plaque proves inaccurate, that is it is not meeting all the above-mentioned features, another plaque should be made and the quality requirements checked again. If the wax was still oscillating on the dental arch, this would give the certainty of working on a model not faithful to reality, because it relates to an inaccurate impression: then it is needed to start from a new impression. Before moving to the registration of the RP, the mating of the lower arch with the wax sheet has to be checked. It is advisable to ask the patient to perform movements of laterality and protrusion against the wax and to remove any wax areas that can
create interferences. The registration is performed at the chair, after instructing the patient to simulate some recordings, and after having deconditioned the proprioceptive system with mandibular movements of protrusion and retrusion, without dental contact. After that, the masticatory system of the patient will be relaxed using cotton rolls placed in the lateral zones of the arches. Another deconditioning system can entail the use of one of the three wax sheets available for the registration. At this point the RP can be recorded; RP wax will be rebased on the side of contact with the lower arch, with Aluwax wax, just in three points: the first on the incisors and the other two, one right and one left, in the molar area. Before removing the cotton rolls the patient is invited to swallow, then the position is registered, visually controlling the contact area between the lower incisors and the Aluwax wax. The patient is then asked to make small movements of opening and closing without translatory movements, so as to verify the repeatability of the indentations. Indentations will then be cooled with compressed air, finally asking the patient to open his mouth offhand. It could happen that the first registration cannot detect all the three contacts on the Aluwax wax: in this case the thickness of the wax has to be increased in correspondence to the missing points and a new registration has to be performed. After that, with the patient still at the chair, the mating face of the three points with the lower model has to be checked. Having already mounted the lower model on ICP previously, an additional check of the relations between the two arches can be done on the CPV; this will allow evaluating in few minutes the difference between the condyle’s position in ICP and in RP. This phase does not imply the need of plastering the model in the articulator, in RP position (Fig. 2.42).
Fig. 2.42 RP wax with the three tripod indentations.
In case of patients with deep bite, the wax would have an exaggerated posterior thickness, with a too high vertical dimension of registration, due to the immediate contact of the lower incisors on the wax sheet. Therefore, the incisors will not be registered, giving the lower jaw the possibility of pointing out a smaller vertical dimension of registration. Thus, only the indentations in the left and right side sectors, posteriorly to the canine teeth, will be recorded
(Figs. 2.43 to 2.44).
Fig. 2.43 Variant of the wax sheet up to the premolars, in case of patients with deep bite. During the RP recording, the incisor group is excluded from the registration.
Fig. 2.44 Indentations on Aluwax wax.
Fig. 2.45 Horseshoe shape’s variant: it avoids the interference with the posterior dorsum of the tongue without compromising the stability and resistance of the wax sheet.
Fig. 2.46 Tripod indentation: recording only three contacts, registration errors due to the conditioning of the proprioceptive system are eliminated to the maximum.
Fig. 2.47 In the full technique the high number of indentations and the impossibility of controlling the hardness and stability of the wax increases the errors’ probability in the detection of the RP.
In case of replacement of prosthetic devices, of which the clinician wants to check the therapeutic position, a single wax sheet will be used, so as to have a thin thickness, retaining by the way the rigidity of the wax sheet. Alternatively, the registration can be made by using a vacuum formed mask with maximum thickness of 0.5 mm. In this way the errors due to a registration with hinge axis’ translational components, caused by the thickness of the registration support, will be as much as possible eliminated. In presence of adequate dental supports the three stop points will be sought: one anteriorly and two posteriorly, passively indented in Aluwax wax, without exposure of the Beauty-Pink. Once the RP is recorded, the upper and the lower models will be assembled according to the ratio obtained by taking into account the space created between the arches by the thickness of the wax interposed there (Figs. 2.48 to 2.50).
Fig. 2.48 Mounting of the lower model with RP wax. Opened articulator with accessory for mounting the lower model and lower model (prepared with three pins) interfaced to the upper model by means of the RP registration wax.
Fig. 2.49 Detail of the model base with the 3-pins and model boxing with gummed paper. Notice the choice of the gray distance block to reduce the plaster thickness.
Fig. 2.50 Mounted models on the articulator with RP wax: noting the divergence between the articulator branches: it is due to the incisal pin placed at +7 mm, to compensate for the wax thickness.
The space between the dental arches can also be measured at the premolar level: in this case its value will double and the incisal pin will be risen from the zero point to this value. In this way, more precision is obtained: once the wax is removed, bringing the arches at the first contact, i.e. Retral Contact Point (RCP), the incisal pin position will be set to zero, either slightly above or below it. Closing the articulator, the first thing to evaluate is the position of the first dental contact (which will not always be in the posterior area), the incisal pin’s height and the new occlusal relationship between the arches (Fig. 2.51). During orthodontic treatment, a replacement of models in RP is key to an occlusion assessment before finalizing the case, because the clinical evaluation of the occlusion by itself, done through articulating papers, is not enough and can be misleading.
Fig. 2.51 Articulator with arches at first contact, after having removed the registration wax: in this case the branches are parallel again since the pin goes back to the zero point or close to it, with first contact to the incisors’ level.
In fact, when comparing the results of these two procedures, sometimes they are the opposite: inside the mouth, with articulating papers, an occlusal contact is highlighted, due to tissues’ resilience (TMJ); the assessment of the RP on articulator highlights instead the need for support. The articulating papers would lead to create a sub-occlusion since the clinician, eliminating the contacts with the selective grinding, would cause a loss of the posterior support by creating joint compressions. The “mounting in RP” technique instead, allows pointing up the need to create the right occlusal support to keep the TMJ unloaded.
Photographic documentation of the patient and of models The photographic support should be considered as a key part of the integrated diagnostic path. First of all, the pictures must show the functional aspect necessary for the diagnosis, both in the initial phase and for judging the final result. For example angled or reduced shots with close-ups on details that decontextualize the teeth from the rest of the mouth, usually hide unattractive aspects that are important instead for the functional diagnosis (Fig. 2.52).
Fig. 2.52 Material needed for the photographic documentation. Cheek retractors of different shapes to take frontal and lateral occlusal picture with mirror, and black masks (contrasters).
Starting from high photographic standards, with high-definition formats, also using the panoramic picture of the dental arches, some shots can be reworked, with the help of PowerPoint or Keynote, creating images that give more importance to the aesthetic aspect, which is always correlated, however, with the functional one. When taking pictures, it is fundamental to think functionally, not aesthetically; so that the photographic documentation can be used to make a diagnosis, and it will also be valid from the forensic medicine’s point of view. For years, a dynamic photographic documentation has been added to the static documentation, with footage referring to different therapeutic stages (before-during-after), for what concerns the aesthetic and phonetic aspects and functional movements. The images and footages, via memory cards or even through online systems for large file sending (e.g. Dropbox), can be shared with the laboratory, confirming the importance of an effective communication between the dental practice and the dental laboratory. Only if well organized, the photographic documentation will become a routine practice, especially when it comes to witness the various stages of progression of the treatment. The photographic protocol provides a standard set of five pictures of the face, integrable with other shots, depending on the particular requirements of each case. In particular, the photographic protocol must contain: a frontal picture of the face and a right lateral one performed with arches in contact and closed lips; a frontal picture and a lateral one with forced smile; finally one picture of the right side of the face, with a 45° angle, with a spontaneous smile (it will be important to include in this picture’s frame the lateral angle of the left eye, Fig. 2.53). Fig. 2.53 Photographic protocol of the face.
Fig. 2.53A Face, frontal.
Fig. 2.53B Frontal face with smile and contact between dental arches.
Fig. 2.53C Face, Lateral.
Fig. 2.53D Lateral face with smile and contact between dental arches.
Fig. 2.53E Face, right side, angled at 45° degrees with a spontaneous smile.
Facial pictures are indispensable for the aesthetic evaluation of the face, in order to detect its symmetries or asymmetries on the reference axes, namely the vertical, the transversal and the sagittal ones (Figs. 2.54 to 2.55).
Fig. 2.54 Plans and reference lines of the patient’s face on the frontal plane: Z-axis that provides the vertical parameter to the right and to the left, Y-axis that provides instead the transversal parameter to the right and to the
Fig. 2.55 Maps and reference lines of the patient’s face on the sagittal plane: X-axis that identifies the sagittal plane from the front to back (antero-posteriorly), Z-axis that provides the vertical parameter. The red triangle identifies the VD, the green line shows the profile evaluation according to Ricketts, the yellow line indicates the anterior-posterior position of the mandible.
In the evaluation of the pictures, the main reference point is the midline of the face (Z axis) and its horizontal perpendicular (Y axis), which may or may not coincide with the bipupillary line (Fig. 2.54). Then are identified lines that define the alignment of the upper incisors’ edges, the line joining the labial commissures and the line connecting the left and the right acoustic meatus; finally, the dental midline and the smile line. Further information can be deduced by integrating the documentation with other shots aimed to highlight the initial micro and mini-aesthetic appearance. The facial picture’s shot will also include the shoulders, so that it will be possible to assess head and cervical spine’s postural aspects, both on the frontal and on the sagittal plane. In the facial lateral picture the ear flap must be clearly visible, as it is useful for tracking the reference planes: the Frankfurt plan, the axis-orbital or Camper’s one. The asymmetries highlighted in the pictures have to be compared to those found with the anatomical face bow and the cephalometric x-ray of the skull, latero-lateral and anterior-posterior (Fig. 2.56).
Fig. 2.56 A small angle of the head towards the left side might suggest an asymmetry, however not confirmed by the perpendicularity of all the horizontal references to the face midline (red line).
It must be assessed whether the asymmetries detected with the anatomical face bow depend on a postural asymmetry of the head, or, as noted talking about the face bow, on a nonsymmetrical placement of the acoustic meatus. If the anatomical face bow proves perpendicular to the median line, both on the frontal and on the transversal planes, a rotation or inclination due to posture of the skull must not be corrected. With therapy, a postural repositioning of the head will be obtained and the prosthetic device will be perfectly symmetrical in the space, without rotations or inclinations (Fig. 2.57).
Fig. 2.57 Correct head posture on the Y and Z axes: the face bow inclination to the right is due to the lower right acoustic meatus.
The intraoral photographic protocol consists instead of six shots: a right lateral, a frontal, a left lateral, one regarding the right over-jet and over-bite, one of the upper arch and the last one of the lower arch, executed by means of a mirror. The focus point, located at the first upper premolar level, will allow a shot going from the mesial face of the contralateral canine to the second ipsilateral molar (Figs. 2.58 to 2.59). Fig. 2.58 Patient’s position, cheek retractors’ position and chair assistant hands’ position on the shot.
Fig. 2.58A Frontal.
Fig. 2.58B Lateral.
Fig. 2.58C Right over-jet and over-bite.
Fig. 2.58D Superior arch with mirror. Fig. 2.59 Intraoral photographic protocol.
Fig. 2.59A Frontal.
Fig. 2.59B Right over-jet and over-bite.
Fig. 2.59C Lateral right.
Fig. 2.59D Lateral left.
Fig. 2.59E Upper arch.
Fig. 2.59F Lower arch.
The occlusion ratio of the upper first molar with the lower first molar must be visible in the picture, and the occlusal plane that goes from the first molars to the incisors must be horizontal. The shot must be perpendicular to the dental arches’ plane, with no upwards or downwards angles. The 45° angle from the bottom to the top gives the possibility to better assess the occlusion, since it reveals the actual relationship between the lower stamp cusps (active centric) and the upper fossae (passive centric), as well as the dental class relationship. In case of a cross bite, given that the occlusal relationships between the two arches are reversed, the camera angle will be the opposite, from the top downwards (Figs. 2.60-2.62).
Fig. 2.60 Occlusal relationships in lateral-orthogonal view.
Fig. 2.61 Occlusal relationships in lateral view with an angle of 45° degrees from below. Fig. 2.62 Horizontal and vertical reference plans, focus point for the shots.
Fig. 2.62A Frontal.
Fig. 2.62B Lateral.
Shooting in a standardized way it is very easy to create overlapping sequences of various shots to document the progression of the treatment, from start to finish, especially in orthodontic treatments. The photographic protocol of models mounted on articulator provides the same shots of the intraoral protocol, satisfying this recommendation: in the lateral picture, the shot will have to be perpendicular to the lateral plane of the models in order to better identify the dental class relationship; in that way, the shot of the incisor over-jet and over-bite will be avoided. To highlight the occlusal plane inclination, the shot must be parallel to the horizontal plane of the articulator. Therefore, taking into account these measures, respecting the same settings for the shots of both the intraoral and the models’ pictures, these pictures can be compared for diagnostic purposes. On models, details of the occlusion that are not evident in the mouth due to the presence of soft tissue, that is to say lips and cheeks (Figs. 2.63-2.64), will be visible instead. Fig. 2.63 Photographic protocol of models mounted on articulator.
Fig. 2.63A Frontal.
Fig. 2.63B Lateral right.
Fig. 2.63C Lateral left.
Fig. 2.63D Upper arch.
Fig. 2.63E Lower arch. Fig. 2.64 Comparison between intraoral framing and framing on articulated models.
Fig. 2.64A Pictures of mounted on articulator models (below) executed under the same settings as the intraoral ones (above), with the advantage to stand perpendicularly, being able to see the entire lateral arch to the third molar and the actual inclination of the occlusal plane (red line).
Fig. 2.64B Comparison of the occlusal view between models’ pictures and intraoral ones.
Another important aspect for the diagnostic evaluation of the occlusion are also the pictures of the plaster models framed from the inside. This shot shows that not always a good dental alignment on the vestibular view corresponds to a functional intercuspation. Also for the models will be made a shot from the bottom to the top with 45° angle, for a better assessment of the occlusal relationships (Fig. 2.65). Fig. 2.65 Shots that show better the occlusal relationships.
Fig. 2.65A Shot of models at 45° degrees from below.
Fig. 2.65B Shot of models from the inside.
Cranial x-ray LL, AP, dental panoramic x-ray After having prepared the photographic documentation, the understructure supporting the facial macro-aesthetics will be detected through the X-rays. The initial radiographic standard includes a classic ortho-panoramic examination and two projections of the skull: a right latero-lateral and an anterior-posterior. Having to set up a sort of patient’s identity card, the ortho-panoramic x-ray should be performed on all patients from 6-7 years of age, also to have the chance of making early diagnoses (eg ageneses). The ortho-panoramic, in spite of not being the elective exam to investigate on the TMJ, allows the assessment of important functional aspects regarding the shape of the condyle’s head and directs the clinician towards further diagnostic evaluations (Figs. 2.66-2.67).
Fig. 2.66 Ortho-panoramic x-ray in adult patients with TMJ dysfunction (note the demodelling of condyles’ head).
Fig. 2.67 Ortho-panoramic x-ray in 6-year-old girl, which highlights the agenesis of the lower second premolars (early diagnosis allows implementing a targeted treatment plan).
It would be good to execute the abovementioned x-rays after having taken the photos, having mounted the models on the articulator and after having performed an initial assessment of the RP. Already at this stage, considering all the information inferred from this organic research, information will arise also on the head, neck and mandible’s posture and positioning the patient’s head on the craniostat will not be random. Therefore, forcing the position of the patient’s head in the craniostat’s earplugs (porus supports) has to be avoided. When the right position will be found, the earplugs (porus supports) will be removed from the acoustic meatus, leaving the only support of the nasion: at this point, the clinician will ask the patient to relax and to look ahead, forward, towards the horizon. Achieving this head’s posture, not conditioned by the craniostat, is crucial for evaluating the cervical column, the posture of the head, of the tongue, the hyoid bone and the upper airways’ width. For example, with acoustic meatus not at the same level, both vertically and anteriorposteriorly (position already accounted for when we place the face bow), putting the craniostat’s earplugs (porus supports) in the acoustic meatus has to be avoided because this would produce an angle of the head on the vertical plane towards the side of the higher meatus, and its rotation towards the side of the more anterior acoustic meatus (Fig. 2.68A). Fig. 2.68 Asymmetric Patient on craniostat.
Fig. 2.68A Dysfunctional patient, with obvious asymmetry positioned on the craniostat: earplugs (porus supports) should not be forced into the acoustic meatus; only in this way the two projections AP(b) and LL(c) are able to show the real posture of the head and of the cervical column.
The examination has to be performed with dental arches in contact, in maximum intercuspation (ICP); just in this way this position can be interfaced with that of the models mounted on the articulator in ICP. The same rules apply for the exam with antero-posterior projection. To avoid other influences will be convenient to perform the radiographic examination without shoes. The cephalometric x-rays LL and AP will be used to perform cephalometric tracings, following various authors’ indications, in order to obtain comparable values (Fig. 2.68). For over 20 years the Cadias® system (manufactured by Gamma AG) has been allowed working digitally with the enormous advantage that once cephalometric points are digitalized, the data obtainable from different tracings can be visualized. The possibility of overlapping the cephalometric tracing to the x-ray and to the facial pictures gives further diagnostic possibilities and allows controlling the exact execution of the tracing. These three X-rays are the standard to be used routinely on all patients who must undergo rehabilitative orthodontic implant-prosthetic treatments or splint therapy. More complex and expensive tests such as the Cone-Beam and the nuclear magnetic resonance (NMR) must be proposed only for particular cases, because they are not always useful in order to improve diagnosis and therapy. The importance of having a cephalometric tracing is not just about orthodontics, but all the rehabilitative branches, namely the prosthetic and the implant-prosthetic ones. The cephalometric tracing performed on the latero-lateral cranial x-ray allows making a skeletal classification in the sagittal direction (I, II, III class) and on the vertical one (high and low angle), then to be able to assess the vertical dimension (VD). The cephalometric tracing performed on the antero-posterior cranial x-ray allows to evaluate
the right and left vertical dimension on the frontal plane, making it possible to identify any mandibular lateral deviations (MLD). Therefore, the right latero-lateral and the antero-posterior cranial radiographies are indispensable to obtain a three-dimensional spatial view of the system. The same radiographies play an important role for the aesthetic evaluation, since the facial skeleton, the jaws and the teeth are the load-bearing framework of the macro-aesthetics of the face.
Occlusal analysis of parafunctions: Brux Checker The Brux Checker, introduced by Sato in 2005, is an excellent tool for investigating day and night parafunctions (bruxism and clenching) during the diagnosis, but also for checking the occlusal schemes built on the prosthetic devices without creating occlusal interferences and system constraints. The Brux Checker is a red sheet, of plastic material, thermoformable, it is 0.1 mm thick and, after vacuum pressing, becomes of 0.08 to 0.09 mm in thickness. Electromyographic studies conducted by Dr. Kanji Onodera have shown that the thickness of the Brux Checker does not cause electromyographic alterations to the masticatory muscles that may affect the examination’s outcome. Patients must wear the Brux Checker at night and/or day: this allows observing day and night parafunctions, identifying the occlusal contacts that are not detectable in the mouth or on the articulator by means of the articulating papers, performing standard movements. The evaluation of the contacts on the Brux Checker allows the identification of the arch areas concerned by parafunction that could explain, for example, the occurrence of gingival recession (Fig. 1.11), of sore teeth, the chipping of ceramic prostheses and dysfunctional problems of occlusal nature, undetectable otherwise. The patient will have to wear the Brux Checker just once, during the day or during the night, after having received an explanation and instructions for its correct use (Fig. 2.69).
Fig. 2.69 Pressing of the Brux Checker.
This diagnostic tool is very useful in the rehabilitation phase with the therapeutic provisional,
at the end of the prosthetic therapy to test the ability of controlling the parafunctions of the occlusal scheme created on dentures, and even during orthodontic therapy, before finalizing the case, to check for possible inadequate occlusal schemes. The Brux Checker sheet is impregnated with a red dye on the part oriented toward the opposing arch. During its stay in the oral cavity, the contact areas with the antagonist arch lose the dye and become white-transparent. The location and extension of white areas allow distinguishing the grinding areas to those of clenching and making a classification of the occlusal scheme linked to parafunction. The contact areas are classified as follows (Fig. 2.70): • CI: canine, incisor control; • CI+M: canine, incisor control, plus mediotrusive contact; • CIP: incisor, canine, premolar control; • CIP+M: incisor, canine, premolar control, plus mediotrusive contact; • CIPM: canine, incisor, premolar and molar control; • CIPM+M: canine, incisor, premolar and molar control, plus mediotrusive contact. Fig. 2.70 Various Brux Checker schemes.
Fig. 2.70A CI scheme to the left and CI+M to the right.
Fig. 2.70B CIP scheme to the left and CIP+M to the right.
Fig. 2.70C CIPM scheme to the left and CIPM+M to the right.
Fig. 2.70D Scheme with right and left canine dominance (C), and centric contacts in class I on the stamp cusps and in the fossae.
In case of severe bruxism it is not possible to make a precise classification of the contacts as they appear on all the teeth with very large areas, both on the mediotrusive and on the laterotrusive sides (Figs. 2.71A-B). Fig. 2.71 Pre- and post-treatment control with Brux Checker.
Fig. 2.71A Brux Checker of ICPM+M type (on both sides of the arch) of a patient affected by bruxism before the prosthetic orthodontic multidisciplinary treatment.
Fig. 2.71B Post-therapy: restoration of canine dominance C, with considerable reduction of the entity of bruxism.
The Brux Checker is very useful to monitor the patient’s tendency to establish a parafunction in the long run, so it is possible to use it to make early diagnosis and targeted therapy, without waiting for the onset of symptomatology or possible damages to the tooth structure or the prostheses. The occlusal scheme detected with the Brux Checker, along with the pin model according to Slavicek, are very useful to build in articulator the sequence of tweaks to be done in the mouth, in the clinical cases that need to be treated with selective grinding. The Bruxchecker mask can be used instead of the wax sheet to execute the occlusogram, i.e. to test functional movements on the patient.
CPM and CPV analysis of the mandibular position The right and left hinge axis location and the left sub-orbital point lead to the definition of the axis-orbital plane, detectable, as we have already seen, with a kinematic face bow, used to transfer the upper model on the articulator. In this way, the models are placed in a welldefined system of spatial coordinates, given by individual cranial (left sub-orbital point) and articular (right and left axis) parameters. Once the lower model is mounted on articulator in the two positions, ICP and RP, the threedimensional position of the mandible relative to the maxillary bone can be evaluated and, consequently, the three-dimensional spatial position of the condyles (hinge axis) in the various reference positions. To do this, additional auxiliary equipment is needed: the condylar position measurement (CPM), to use with the articulator; the condylar position variator (CPV), which is similar to an articulator, with condylar housings separable in the three spatial planes (Figs. 2.72-2.74).
Fig. 2.72 Articulator with models mounted in ICP to which the condylar housings have been removed and in their place CPM accessories have been inserted.
Fig. 2.73 Models mounted on articulator in RP position. Fig. 2.74 Evaluation of right and left condylar position (CPM).
Fig. 2.74A Right flag showing the difference of the condylar position between ICP (blue dot) and RP (red dot).
Fig. 2.74B Left flag.
Fig. 2.74C Variation in condylar position on the Y axis (horizontal): the mandible is moved by 2 mm to the left
The CPV, in addition to allowing the measurement of the condylar position between ICP and RP, also permits to vary the condylar position in TRP and consequently the mandibular position with respect to the upper jaw in the three spatial dimensions (Fig. 2.75). Fig. 2.75 Evaluation of the condylar position on the CPV: the variation of the condylar position is read on the millimeter scale with respect to the three spatial axes.
Fig. 2.75A Models assembled on the CPV through the RP wax.
Fig. 2.75B Reading of the values obtained on the Y axis
Fig. 2.75C Reading on the right X- and Z-axes.
Fig. 2.75D Reading on the left X- and Z-axes.
In order for this procedure, based on a spatial coordinates’ system, to be reliable, a starting point of reference is needed: it will be called “zero point” and it will be identified with the position of maximum intercuspation ICP. This “zero” position will be found on models mounted on articulator at ICP and on the LL and AP x-rays, since they are all executed in ICP. Thus, the ICP is the “zero” point from which to move (following the system of spatial coordinates) for reaching the therapeutic position TRP with the help of the CPV.
Patient’s interview: first diagnosis The interview with the patient comes as a conclusion of this first phase, for illustrating the initial diagnostic evaluation of the case and proposing the treatment plan and the relative estimation of costs. While presenting the case to the patient, the clinician will make use of digital and analog supports.
It will still be important to complement the digital format with a hard copy of the PowerPoint presentation, that can be used to make the explanation to the patient clearer, by means of diagrams and drawings, patient who can bring this documentation at home, thus having the possibility of reread it and reflect on it. The interview will be held in the private practice, even in front of any accompanying person the patient has decided to take along with her/him. At the same time, different therapeutic hypotheses, designed to definitively resolve or to stabilize the problem, will be presented. If the initial goal has to be the resolution of the acute symptoms, an initial therapy with splint, selective grinding, pharmacological and physiotherapeutic aids will be proposed. In second instance, the need for a multidisciplinary complex treatment and, consequently, for a further diagnostic study, which is identified with the expression “clinical and instrumental analysis 2” (and explained below), will be illustrated.
Clinical and instrumental analysis 2 Gnathologic chart
Through the “clinical and instrumental analysis 1” signs and symptoms have been highlighted, keeping in mind the indicators that are listed on the gnathologic chart prepared by the Vienna school (indicators that allowed a first classification of the disease the patient is suffering from). Now the “clinical and instrumental analysis 2” will complete the clinical analysis by means of an accurate compilation of the chart (folder) itself. Below there is a list of the components of what will become an essential document for the clinical diagnosis, of fundamental value from a forensic point of view. • General medical history (Fig. 2.76A). • Medical history related to the dysfunctional problem: the patient get asked a series of questions to which he/she will only give a negative or affirmative answer. • Starting from the obtained answers, the clinician will ask to the patient to give an evaluation of the symptom with a positive feedback on the basis of the values 1 (mild), 2 (medium), 3 (severe). • From the average of the measured values, a reference parameter called occlusal index will be derived, index that on a scale from 1 to 3 quantifies the problem as mild, medium or severe (Fig. 2.76B). • Muscular and articular assessment: includes palpation of the masticatory muscles (inside and outside the mouth), of the muscles of the upper and lower cervical area and of those of the shoulders, and of the right and left temporomandibular joints (TMJ). Any evidence of hypertrophy or muscle contractures will be noted separately. The temporomandibular joint examination includes the palpation of the lateral pole in statics and in rotation, the palpation of the posterior pole, and the palpation of the ligament of the temporomandibular joint area. The assessment is made by comparing the left and the right side, with a value of 0 in absence of symptoms, with a value of 1 for mild symptoms, and values of 2 and 3 for medium or severe symptoms (Fig. 2.76C). • Innervations’ assessment: will focus mainly on palpation of the emergency points of the three branches of the trigeminal nerve. Also in this case the symptomatology will be classified according to what reported by the patient: a value of 0 in the absence of symptoms, 1 in presence of mild symptoms, 2 for symptoms of medium entity, 3 for strong
ones. Even at this stage the comparison between the left and the right side has to be made (Fig. 2.76D). • Mapping and evaluation of chronic pain: the patient will possibly indicate to the clinician chronic pain areas that will be mapped on the body scheme kept in the chart. As a specification, “chronic pain” is defined as a pain that has persisted for more than six months (Fig. 2.76E). • Occlusal scheme and occlusogram: allows the evaluation of the occlusal contacts (in centric, protrusion, and right and left mediotrusion) and eventual wear facets (Figs. 2.76F-G). Fig. 2.76 Gnathologic chart.
Fig. 2.76A Chart section with questions related to the general medical history.
Fig. 2.76B Chart section with questions related to the dysfunctional problem in order to calculate the occlusal index.
Fig. 2.76C Chart section on muscular palpation and TMJ palpation.
Fig. 2.76D Chart section on the evaluation of cranial nerves, mostly the three trigeminus’ branches.
Fig. 2.76E Chart section on chronic pain’s mapping.
Fig. 2.76F Upper arch occlusogram.
Fig. 2.76G Lower arch occlusogram.
Recording of mandibular condylography (Cadiax®system)
It is now the time to execute the electronic condylography, which is the digital evolution of analog panthografic tracing. An indispensable condition for its proper execution and for using
the data that it will provide, is the right location of the individual hinge axis. The electronic condylography with CADIAX® system allows to investigate the dynamics of the temporomandibular joint, to extrapolate the data and to evaluate them from a threedimensional dynamic point of view: these data will be used first for diagnostic purposes, then for the individual setting of the articulator. At birth, the temporomandibular joint (TMJ) is flat: when teeth erupt (functional interference) it begins to mold itself under the influence of the teeth themselves and of their shape (genetically predetermined) and position, creating a muscular and structural adaptation of the system. At this point the temporomandibular joint will find its configuration, with characteristics defined by the inclination value (SCI) and by the value of the Bennet movement. Once registered through electronic condylography, these data will be used for the reconstruction of the patient’s occlusal system, according to individual functional parameters (Fig. 2.77).
Fig. 2.77 Diagram illustrating the registration of the condylar path during protrusion and retrusion movements. Condylograph’s components
The condylograph consists of a cranial bow and a mandibular one. The cranial bow is stabilized to the skull: two electronic flags are attached to it for the registration, as well as the system of spatial coordinates X, Y, Z. The mandibular bow instead is anchored to the lower jaw with a para-occlusal clutch and has electronic styles for recording the movement on the flags of the cranial bow. Everything is connected to the PC and processed by the CADIAX® software (Figs. 2.78-2.79).
Fig. 2.78 Condylograph positioned on the patient, ready for the registration. Note the cranial bow stabilized to the skull and the electronic flags fixed on it, the mandibular bow connected to the mandible through the para-occlusal clutch and the electronic styles for the recording of the movement.
Fig. 2.79 Detail of the recording styles connected to the mandibular bow, in contact with the electronic registration flag. Para-occlusal clutch
Since the aim is to use the condylography for diagnostic purposes, for a correct execution of the examination it is necessary a para-occlusal clutch for anchoring the mandibular bow to the lower jaw, a spoon of para-occlusal type and that leaves the possibility to the two dental arches to occlude and disclude, without interferencing with the clutch itself. With adequate tricks the para-occlusal clutch can be used even in severe cases of deep bite, avoiding the incisal sector and allowing arches to close in ICP, without letting the clutch to interfere (Fig. 2.80). Fig. 2.80 Typologies of para-occlusal clutches.
Fig. 2.80A Para-occlusal clutch built on the plaster model.
Fig. 2.80B Para-occlusal clutch in case of a severe deep bite.
Fig. 2.80C Para-occlusal clutch for registration in a patient with full denture.
It is also possible to use an occlusal clutch that covers the lower jaw’s occlusal surfaces. This method prevents the jaw to go in ICP with the maxillary arch, producing a separation
between the arches, the larger, the more pronounced is the deep bite. Consequently, also the condyle’s position will be more advanced along the articular eminence path, making a movement which, in addition to the rotatory component, begins to also present a certain entity of translatory component (Fig. 2.81). The registration with the occlusal clutch, which involves maintaining the arches separated, is not adequate for the individual hinge axis location since, being the lower jaw already with a certain degree of opening, it is already beyond the pure rotational movement necessary for the purpose. In the recording thus the first few millimeters of the initial part of the tracing will be missing, so that the obtained information will not be adequate either for the diagnosis’ definition nor for the articulator’s setting. To the limit, this procedure can be used only for the aim of setting the articulator for healthy patients. Fig. 2.81 Occlusal clutch.
Fig. 2.81A Occlusal clutch on models on the articulator showing the starting position with separate arches (excessive separation because of the deep bite).
Fig. 2.81B Advanced hinge axis position on the path (red dot) because of the mouth opening due to the clutch: in an already short path the first 3-4 mm go lost, instead of their importance in defining characteristics at diagnostic level.
In contrast, the para-occlusal clutch allows the localization of the individual hinge axis, the execution of a complete examination and the obtainment of condylographic tracings sometimes able to highlight pathological aspects in apparently healthy and asymptomatic patients. Registration of the articular dynamics
After the electronic localization of the hinge axis, the protocol provides for the registration of the mandibular movements unguided and without dental contact, according to the following sequence: 1. registration of the protrusion-retrusion path; 2. registration of the right mediotrusive path (left laterality); 3. registration of the left mediotrusive path (right laterality); 4. registration of the opening-closing path; 5. registration of free movements’ path. The first three movements are indispensable to derive the numerical data necessary for the individual setting of the articulator. The registration’s starting point is in RP position, i.e. with the dental arches in disclusion. It is recommended to execute the same tracings taking as a starting point the position in ICP, in order to compare them with those starting from the RP (Fig. 2.82). Fig. 2.82 Above: the classic tracing in the three spatial dimensions; below: the spatial movement of the hinge axis with (below, right) and without (below, left) mandibular scheme.
Fig. 2.82A Movement of protrusion and retrusion (P-R).
Fig. 2.82B Mediotrusion right movement (Mediotrusion Right M-R).
In complex or doubtful situations the standard tracings will be integrated with further ones related to: • bruxism; • swallowing; • phonation; • mastication; • assessment of the mandibular position (MPI) and of the therapeutic position (TRP); • standard movements performed with dental contact with incisors’ guidance in protrusion and with canine guidance in mediotrusions, starting from the maximum intercuspation position. The system allows the carrying out of endless recordings for each single movement, in order to be able to check the repeatability of the tracing (Fig. 2.83).
Fig. 2.83 Screenshot of the protrusion and retrusion tracing with overlapping of the articulator’s condylar housings; upper part: view on the horizontal plane on which the movement on axes X and Y is registered (Bennett movement in asymmetrical movements and delta Y in symmetrical movements); lower part: view on the right and left sagittal plane on which is registered the path in X and Z axes. Evaluation of condylographic tracings
The evaluation parameters relate to the static and dynamic aspects of the resulting tracings. From a static point of view the evaluation is based on: • quantity; • quality; • characteristics; • symmetry. Quantity: expresses the length of the tracing from the starting point RP to the point of maximum excursion. It is classified into: reduced (less than 8 mm), normal (between 8 mm and 12 mm), increased (greater than 12 mm) (Fig. 2.84). Fig. 2.84 Evaluation of quantity.
Fig. 2.84A Opening and closing tracing with increased quantity, asymmetrical in the transverse plane (delta Y) and of poor quality.
Fig. 2.84B Protrusion and retrusion tracing of reduced quantity due to a bilateral joint locking.
Fig. 2.84C Protrusion and retrusion tracing with increased quantity. The non-return to the starting point (red arrow) indicates that the muscular system tends to hold the mandible in a forward position of about 2 mm.
Quality: expresses the linearity of the track, the possibility that the incursive and excursive path are overlapping. It is classified: excellent, normal, low (Fig. 2.85).
Fig. 2.85 Tracing of poor quality, asymmetrical with mutual click on the left (red arrow).
Characteristics: describe the shape of the tracing that should be concave ahead; regarding this parameter the following features are possible ones: concave at the front, straight, change in shape (Fig. 2.86). Fig. 2.86 Characteristics’ evaluation.
Fig. 2.86A Protrusion and retrusion tracing, straight, asymmetric to the sagittal and transverse planes.
Fig. 2.86B Protrusion and retrusion tracing, asymmetric, concave to the right and straight to the left.
Symmetry: concerns the symmetry or asymmetry of the tracings between the left and the right side for what concerns quantity, quality, characteristics, angle. The symmetry concerns only symmetrical movements of opening and closing and of protrusion and retrusion. Because a perfectly symmetrical patient is not normal, slight variations of the aspects concerning the symmetry can be considered normal (Fig. 2.87). Fig. 2.87 Symmetry’s evaluation.
Fig. 2.87A Asymmetrical opening and closing tracing on the transverse plane, of increased quantity and poor quality.
Fig. 2.87B Bruxism tracing, symmetrical by inclination, quantity and quality. Its upper and backward extension relative to the reference position shows a compression on the top and on the back of the temporomandibular joint (TMJ) during parafunction.
From a dynamic point of view, the evaluation must include: the speed of the movement, the rotational and translational components of the hinge axis, the hinge axis movement in both the incursive and excursive phase (noting that the right side data should always be compared to those of the left side). From the diagnostic point of view the condylographic tracings must be evaluated by integrating them with all other diagnostic data which relate to the stomatognathic system as a whole, never separately. The assessment of the condylographic tracing performed by means of digital equipment allows to evaluate the dynamic aspect of movement, which could not be evaluated with the classical analog tracing (Fig. 2.88).
Fig. 2.88 Comparison between analog (left) and digital (right) protrusion and retrusion tracings. The digital path allows highlighting the three-dimensional aspect of the movement and other aspects as the mutual click to the right (red arrow) and the back-surtrusion to the left (red circle).
Final evaluation, diagnosis and treatment plan Diagnosis
The diagnosis provides for the development, evaluation and benchmarking of condylographic and cephalometric data, of models mounted on articulator, Brux Checker, gnathologic chart. Treatment plan
To the patient will be proposed a separate treatment plan in two phases. Initially, a functional intervention (mandibular repositioning) consisting in programming with the VTO (visual treatment objective) the management of the functional prosthetic space will be advised; only at a later time will come the definition of the purely rehabilitative multidisciplinary treatment plan. The animated VTO using the Cadias® software allows explaining to the patient her/his functional digital project, regardless of aesthetics, in order to make her/him understand that the aesthetic objective can be properly pursued, managing the functional prosthetic space (Fig. 2.89).
Fig. 2.89 VTO (Visual Treatment Objective) on which the therapeutic position is simulated, taking into account all the changes regarding the functional parameters (VD, location and inclination of the upper and lower incisors, occlusal plane inclination) as shown on the right table.
If all clinical cases are systematically documented will not be difficult to find another case similar to the one under analysis, which can help illustrating and foreseeing what the final result will be. Using PowerPoint or KeyNote is essential to illustrate the proper treatment plan to pursue, with animations on the ortho-panoramic x-ray. In this phase the digital modelling representing the implants and the teeth, or the possible crowns, will help (Fig. 2.90). This phase should be managed in a personalized and easy manner, without making use of specific programs. The Vienna school’s philosophy allows following the same diagnostic and therapeutic process for all the rehabilitative branches of dentistry, including orthodontics. In the light of what explained above, the electronic condylography proves to be an indispensable examination also for the orthodontist. Fig. 2.90 Final interview with the patient.
Fig. 2.90A Illustration of the diagnosis and of treatment plan to the patient.
Fig. 2.90B Treatment plan scheme, which involves the insertion of implants, crowns etc.
Facial macro-aesthetics related to the mandibular position Introduction In dental rehabilitations, aesthetics and function are often considered as opposed. Without any doubt the expectations of a patient who is about to start a rehabilitation program are mainly oriented to privilege the aesthetic factor. It can happen therefore that the clinician is guided by the need of meeting those expectations by overshadowing the function. In what follows, it will be clarified how aesthetics and function have to be considered in a complementary manner, since together they offer benchmarks able to optimize the success of the designed treatment plan. The clinician will be responsible for letting the patient perceive that behind every aesthetic need, the functional need must find its adequate solution and stability. Consider a case of rehabilitation of a person with severe tooth tissue destruction due to parafunction. A treatment plan exclusively based on the aesthetics restoration as the final result in itself might not always lead to the re-establishment of a proper function, but more often the intervention will reproduce the same situations that were the cause of the problem. Always referring to the same case, the problem solution could be entrusted to the dental laboratory requiring a diagnostic wax-up, mistakenly believing that the problem is solvable thanks to what models tell. It is, however, always and exclusively a clinician responsibility to research the causes of a deviated midline (LM) and to look for the possible strategy to correct it by repositioning the mandible. It is therefore unthinkable that dysfunctional problems can be solved with tricks or technical skills; these problems will be addressed first and foremost eliminating or reducing the causes that generated them. Thus before making any aesthetic programming, whether analog, digital or mixed, the future therapeutic position must be determined following the method indicated in the previous chapters, so that the project is able to anticipate and specify the final result. Clinical cases treated with this method and monitored in the long run (15 years) allow affirming that from the dental point of view the macro-aesthetics of the lower third, and therefore of the entire face, depends on the position that the mandible assumes in the three spatial dimensions. Given this basic assumption, also the consequent micro-aesthetics the incisors’ group and of the lips will be closely related to the mandibular position, i.e. to the system’s vertical dimension (VD). In what follows are listed the useful tools to realize the therapeutic path of compared aesthetics and function.
Cybernetic system The cybernetic scheme of the masticatory organ by Professor Slavicek (Fig. 3.1) clarifies all the doubts about the alleged conflict between aesthetics and function. It reiterates in fact that the
stomatognathic system (masticatory organ) performs certain functions, the aesthetics among them. According to the same scheme the aesthetic function (the appearance) interacts with the external environment, resulting in a state of well-being or psychological distress of the patient. Therefore, the aesthetic function directly affects the psyche, correlating the aesthetic aspect with the central nervous system (CNS). The patient’s face as a whole, then the aesthetic appearance, is subject to an external perception which is individual, subjective, disconnected from objective stereotyped canons. Even the stress management function carried out by bruxism and clenching is a mechanism that allows lightening the mental load generated by the external environment. Of course this function of the masticatory organ manifests its effects, weighting on the occlusion and on teeth, altering their shape and consequently the aesthetics of the smile (Fig. 3.1).
Fig. 3.1 The diagram shows how the external environment (blue arrow) has an influence on the psyche and, through parafunctions (unloading mechanism of emotional pressure), on teeth (occlusion) and consequently on articular and muscular structures and on aesthetics (in respect of the damage to the tooth structure). It is clarified in this way the connection between aesthetics, environment and repercussions at psychological level (CNS). CMS = CranialMandibular system, TMJ = Temporo-Mandibular Joint, NMS = Neuro-Muscular system CNS = Central Nervous System. (From Slavicek, modified)
On the other hand, the aesthetic is closely linked to the occlusion since only a proper management according to functional principles is able to lead to a situation of global welfare of the body, respecting the muscular and articular system and generating a high level of functionalaesthetic satisfaction (Fig. 3.2).
Fig. 3.2 The diagram shows how a functional management of the occlusion, respecting the TMJ and the NMS, is able to create a good aesthetics, to control parafunctions and, therefore, to have a positive influence on the psyche. TMJ = Temporo-Mandibular Joint. (From Slavicek, modified)
This means that the smile aesthetics is an inevitable consequence of a correct functional approach that not only affects the management of the incisal group, but also, and before, it is capable of affecting the management of all the rehabilitation functional space (prostheticorthodontic-implant prosthetic). So the smile aesthetics is closely linked to the mandibular position and consequently to the vertical dimension (Fig. 3.3). Fig. 3.3 Change in the perception of the global macro-aesthetics of the face through a process that primarily provides the function management, with change in VD and then in the mandibular position.
Fig. 3.3A Pre-treatment macro aesthetics.
Fig. 3.3B Post-treatment: the obtained macro aesthetics clinically confirms the path presented in Fig. 3.2.
Surely the aesthetic function is the one that generates most interest both in the clinician and in the patient. The masticatory organ performs in fact other functions in addition to the chewing one. Language, posture, breathing, swallowing, stress management (parafunctions) have during the 24 hours a very high frequency, far greater than the pure act of chewing; the clinician must then take into account all these functions (Fig. 3.1).
In 1984 Professor Slavicek affirmed that the parafunctions bruxism and clenching are a relief valve for psychic stress, then concluded by saying that these can be classified as normal masticatory organ functions. Recent studies of Professor Sato demonstrate the close correlation between stress, bruxism and heart rate, widening even more the panorama that connects the masticatory organ to the rest of the organism. All this highlights the close link between masticatory organ and psyche, and in this relation, the main role is played by the occlusion.
Dental and facial aesthetic canons For a proper evaluation of the aesthetic parameters of the patient’s face, and as a consequence of her/his mouth, points of reference have to be established framing the patient’s face-mouth-teeth system in the three spatial dimensions: X (sagittal), Y (horizontal), Z (vertical) (Fig. 3.4). From the combination of the detected axes three plans are derived, useful to frame the face macroaesthetics. The Y horizontal axis with the Z vertical axis forms the frontal plane; the X sagittal axis with the Z vertical axis forms the sagittal plane; the Y axis with the X axis forms the horizontal plane (Fig. 3.5). On the frontal Y-Z plane it is possible to detect mandibular movements to the right or to the left (mandibular lateral deviations, MLD), the differences in vertical dimension between the right and the left part, the inclinations of the head’s posture to the right or to the left. Still, this is the plan on which the face’s midline takes place, midline which constitutes a reference point for the upper and lower dental midline.
Fig. 3.4 Position of the face in the space according to the three axes X-Y-Z. Fig. 3.5 Position of the face in the three spatial planes.
Fig. 3.5A The three reference spatial planes on which should be seen the macro aesthetics of the face.
Fig. 3.5B Frontal plane (green).
Fig. 3.5C Horizontal plane (red).
Fig. 3.5D Sagitta plane (blue).
On the sagittal X-Z plane, the vertical dimension of high-low angle (deep and open) and the skeletal classes I, II, III are evaluated instead.
The horizontal X-Y plane seen from above (12 o’clock) and seen from below (6 o’clock) allows evaluating the mandibular position and the upper arch with respect to the midline (ML). Moreover, it allows the evaluation of the harmonic relationship between the upper and the lower lip at rest (rest position) and in various smile’s levels, which also derives from the congruity of the upper and lower dental arches. Regarding the main reference lines on the frontal and on the sagittal planes look at to Figs. 2.54 and 2.55; the same lines can be displayed with the vision at 12 o’clock and at 6 o’clock on the front-horizontal plane (Figs. 2.35B-2.36A, Fig. 3.6). Fig. 3.6 Face view on the horizontal plane.
Fig. 3.6A Views of the horizontal plane at 12 o’clock, very useful to frame the lips aesthetics in relation to the shape and width of the upper and lower dental arches (full denture case).
Fig. 3.6B Views of the horizontal plane at 6 o’clock, very useful to frame the lips aesthetics in relation to the shape and width of the upper and lower dental arches (full denture case).
The same planes, as said in Chap. 2, are found on articulated models, with their red mounting plates and gray distance block as provided by the systematic of Reference SL articulator. The reference given by the red mounting plates and by the gray distance block is very useful when working with handheld models for the evaluation of symmetries maintaining spatial references (Fig. 3.7). Fig. 3.7 The three spatial planes on models mounted on the articulator (the same full denture case of Fig. 3.6).
Fig. 3.7A Sagittal plane (X-Z) in which the reference is the top of the distance block (X axis); the OP (red) and the
coronal axis of the incisors (green) can be visually detected.
Fig. 3.7B Frontal plane (Y-Z) in which the horizontal reference is given both by the top of the distance block and by the red mounting plates; the dental midline, the incisors canines and premolars dental axes, the line of the incisor edges can be detected.
Fig. 3.7C Horizontal plane (Y-X): in this case the horizontal reference is given by the anterior part of the distance block. The symmetry of the two half arches, right and left, which is decisive for the support and the symmetry of the lips, can be assessed.
Now the relationship between aesthetics, mandibular position, occlusion and dysfunction will be investigated. The shape of the teeth’s crown is genetically determined, but the management of their position therapeutically is up to the dentist. From the orthodontic point of view, but also from the implant-prosthetic one, it is therefore necessary to learn how to manage the position of the tooth and consequently that of its functional surfaces (occlusal for the posterior teeth, palatal for the incisors and upper canines, incisal edges for the lower incisors and the lower canine’s cusp). To mimic the natural teeth shapes with analog or digital techniques is not enough: these techniques must be integrated into a dynamic system, with individual functional parameters. The aesthetic canons laid down by the “masters” (level of gingival parables, interdental spaces, the zenith of the gingival contour, tooth size, tooth axes) must be taken into account, but their
radicalization to create something visible only for the clinician at a micro aesthetics-mini aesthetics levels makes the treatment more invasive and does not guarantee stability over time. The priority has to be given to all those aspects that affect facial symmetry, related to arches’ symmetry, and visible from interpersonal distance. These aspects are: respect of the horizontality of the upper and lower incisors’ edges, position of the midline, incisors’ axis on the sagittal plane, left and right occlusal planes’ level, the spatial position of the mandible (Fig. 3.8). Fig. 3.8 Case of complex rehabilitation on natural teeth and implants (2007).
Fig. 3.8A While not fully respecting the aesthetic canons, an excellent mimicry’s result was achieved.
Fig. 3.8B From a broader perspective and contextualizing the upper with the lower incisors, details are becoming lesser and lesser evident.
Fig. 3.8C At the facial macro-aesthetics level, the result is excellent and the patient has not been subjected to further surgical interventions, thus reducing the level of invasiveness of the therapy.
Therefore, once the function and the resulting macro and mini-aesthetics are restored, further micro-aesthetics interventions which do not concern the prosthetic device, but the biological tissues on which it rests, will be implemented only if decisive for the therapeutic outcome or if requested by the patient after an adequate explanation on costs and benefits and on possible alternative solutions. “Compromise” situations are acceptable when reached through the artistic abilities of the technician and exploiting properties and characteristics of the available materials. Thus, a camouflage, a mimicry is reached, that makes invisible to the eye of an ordinary observer eventual situations which do not meet 100% the aesthetic parameters of the arch anterior sector (For example: ideal location of the gingival parables, correct proportions between dental crown’s height and width). Three aesthetic levels have to be considered: macro aesthetics, mini aesthetics and micro aesthetics; they are closely related to the mandibular position and consequently to the vertical dimension and to the function. Facial macro aesthetics covers face’s global panorama, this being the tool through which the patient interacts with the external environment. The key elements to consider are: eyes, labial tissue, teeth, facial expression muscles (contraction levels), and of course the evaluation of symmetries in the three spatial planes. Narrowing the view to the dental-labial level and to part of the gingival tissues (e.g. upper smile
line; gum smile) mini-aesthetics can be defined as the proper management of the incisors (the upper and the lower) according to functional parameters, which will create the right support to the labial tissues. Further restricting the view and concentrating it on a single dental element (or maximum on two teeth) the extension of micro aesthetics is defined: it concerns the dental crown (shape, size, color, surface texture, etc.) and the point of transition between the crown and gingival tissues (Fig. 3.9). Fig. 3.9 Macro-mini-micro aesthetics of a metal ceramic rehabilitation after 12 years.
Fig. 3.9A Initial mini aesthetics, 2001.
Fig. 3.9B Mini aesthetics with a panoramic view of arches in ICP.
Fig. 3.9C-D Mini aesthetics with detail of the dental-labial relation of the incisors’ group.
Fig. 3.9E-F Micro aesthetics that highlights the relationship of the crowns with gingival tissues and the characteristics of the material, color, shape and texture of the surface.
The starting point for obtaining an excellent result in all these three levels must be found in a careful assessment of the underlying structure and in a resulting therapeutic project of the vertical dimension, as well as of the mandibular position. The patient’s face from a macro aesthetics point of view has to be divided into three sections (thirds), without forgetting that the relative proportions depend on the underlying support structure; the assessment must be made on the sagittal plane and on the frontal plane, so threedimensionally (Fig. 3.10).
Fig. 3.10 Lateral and frontal view of the division of the face into thirds on pictures and teleradiography. Lower third (green zone): ranging from the sub nasal area, i.e. the anterior nasal spine, to the lowest point of the chin (skin Menton); this area is identified by the functional prosthetic space and by the lower facial height. Medium third (yellow area): goes from the sub nasal area, i.e. the anterior nasal spine, to the line connecting the eyebrows; roughly corresponds to the upper facial height. Upper third (red zone): goes from the line connecting the eyebrows to the hairline.
The lower third depends on the skeletal class and on the vertical dimension and is the only part of the face on which the therapeutic intervention of the dentist has an effect, which consists in the variation of the vertical dimention and of the mandible position on the sagittal plane (skeletal class). It is important to say that, even if the field of action of the clinician is limited to the lower third of the face, intervening on the functional prosthetic space in accordance with the function implies improvements at the level of the other two-thirds, which will find a new harmony with all the facial expression muscles (Fig. 3.3).
Aesthetics and underlying structure If the goal is that of creating a functional rehabilitation the methodology has to change, to obtain the aesthetics starting from the evaluation of the skeletal substructure. It could happen, as mentioned above, that the dentist focuses on the aesthetics decontextualizing if from the whole stomatognathic system and directing her/his expectations and those of the patient exclusively to the anterior-superior sector. Conversely, any prosthetic device will have to be always in line with the skeletal and muscular structure, that is to say, with the dynamic support system, which results critical to the rehabilitation success (Figs. 3.11 to 3.12). From the images of Fig. 3.12 it is clear that the management of the vertical dimension and of the consequent mandibular repositioning is decisive for the aesthetic definition of the lower third of the face.
Fig. 3.11 Overlay of facial pictures to the cephalometric teleradiography on the sagittal plane (left) and on the frontal plane (right) demonstrating that the aesthetics of the lower third depends solely on the underlying skeletal structure (mandibular position) and on the dental position.
Fig. 3.12 Case treated with variation of 8 mm of the VD (initial situation to the left), control after 13 years (right): the variation of the mandibular position has allowed the creation of an underlying support structure, resulting in a complete reorganization of the facial macro-aesthetics, stable in time.
The reorganization of the lips is only due to a functional position of the incisors’ group, possible only thanks to the change in VD of even 8 mm on the articulator’s incisal pin. The main objective of the clinician must then be the search for a correct function, to obtain an unextreme aesthetics, but built according to the concept of mimicry. In this context, the technician can achieve satisfactory results because the clinician will have created the functional requirements that will enable the suitable realization of the prosthetic device.
Skeletal classifications From the orthodontic point of view, but also from the prosthetic and implant-prosthetic one, we have to preliminarily consider the affiliation of the patient to determined skeletal classes according to well-defined percentages, as supported by scientific research. 52% of patients are in Class II (first and second division), 37% in class I and 11% in class III: each of these three classes can be further divided into high and low angle variations. It should be added that all the three classes can include the variant with right or left MLD (Fig. 3.13).
Fig. 3.13 The figure shows the percentages that are allocated to the skeletal classes and the corresponding classification of the dental class. In this classification we must add the low and high angle variants and the MLD.
Belonging to the skeletal class I and having a class I dental relationship it is completely different from saying that the patient is immune from dysfunctional problems. For example, the detection of a I skeletal class on the LL, and of a MLD toward the left side with a dental relationship of I class to the right and of II class to the left, imposes the need for further investigations with an AP x-ray and a subsequent possible diagnostic and postural analysis (Figs. 3.14 to 3.15). Fig. 3.14 Case of left MLD in dysfunctional patient.
Fig. 3.14A Facial macro aesthetics highlighting the MLD to the left side and the inclination of the head axis to the right.
Fig. 3.14B-C-D Intraoral right, frontal and left view: it shows the right I class relationship, the deviation of the ML to the left with torsion of the upper jaw to the left and a II class relationship to the left. Fig. 3.15 Radiographic examinations of the case in Fig. 3.14.
Fig. 3.15A The LL x-ray shows a I skeletal Class with a VD in standard values: only the segment elevation of the right-left mandibular plane with two levels of the OP should raise the dubt of a MLD.
Fig. 3.15B AP radiography confirms what has been shown from the frontal picture and from the intraoral examination.
Fig. 3.15C An examination of the spine shows a postural problem with a scoliosis curve to the right, in the thoracic tract, and a segment elevation of the iliac crests.
Fig. 3.15D In RP, the midline will re-center, highlighting an increased left interocclusal space compared to the right one, as well as the significant segment elevation of the occlusal planes.
In this specific case, just the orthodontic treatment with dental alignment, without programming a three-dimensional repositioning of the mandible (sagittal, vertical and in tilting, further increasing the left VD), would not be able to resolve the problem, exposing instead to high risks of failure. This shows that the diagnosis cannot be the result of a simple classification based on dental relationships, but is derived from cephalometric tracings executed both on the LL x-ray and on the AP x-ray, supplemented with additional diagnostic investigations. In this way, any aesthetic project will never be decontextualized from the functional aspect.
Cadias®tracing on the LL The execution path of the cephalometric tracing is fully digital, thus easily usable. Once the digital x-ray is done (Chap. 2), the file is imported into the Cadias® software, where cephalometric points are individuated, points from which the plans can be inferred. After this, from the convergence of the various plans are derived angular measurements that, evaluated according to several authors (cephalometric comparative analysis), will allow classifying the patient from a skeletal point of view (Fig. 3.16).
Fig. 3.16 The figure shows the Cadias® screen for the digital execution of the cephalometric tracing. On the left side, detail of the cephalometric x-ray that underpins the cephalometric points, on the right side the list of the points to be localized.
The reference cephalometric tracing is that of Slavicek, similar to that of Ricketts except that in the first also dynamic parameters are entered, those arising from condylography (SCI). Cephalometric points, planes and angles will be important to carry out a comparative analysis which takes account of: • aesthetic analysis of soft tissues (lips, nose, chin); • sagittal analysis, from which derives the skeletal classification; • vertical analysis, which involves the evaluation of the vertical dimension with skeletal parameters; • dental analysis borne by the upper and lower incisors; • dynamic analysis (functional), for determining the inclination of the occlusal plan and the inclination of the upper incisor’s palatal surface (S1-S2).
Cephalometric points on the LL tracing Skeletal points
• BA-basion: identifies the lowest point of the anterior edge of the occipital foramen magnum; • HA-individual hinge axis: highlighted by metallic references placed on the skin after locating the hinge axis with the condilograph. (In case of using a statistical hinge axis, its position is given by the intersection between the condyle axis and a straight line that goes from the OR with an angle of 5° degrees with respect to the Frankfurt plane);
• Pr-Porion: the highest point on the contour of the external auditory canal; • S-Sella: the point at the center of sella turcica; • PT-pterygoid: highest and rearmost point of a radiolucent area with drop form, given by the union of the lower edge of the great round foramen and the posterior-superior edge of the pterygo-palatine fossa; • OR-Orbital: the lowest point of the inferior boundary of the orbit; • NA-Nasion: foremost point of the front-nasal suture; • ANS-anterior nasal spine: apex of the nasal spine; • PNS-posterior nasal spine: the final part of the bony palate; • A: rearmost point on the anterior edge of the maxillary bone, below the nasal spine; • B: rearmost point on the anterior edge of the mandibular symphysis; • PM: point on the anterior edge of the symphysis that shows the profile’s change from concave to convex (otherwise findable somewhere between point B and point Po); its position is closely linked to the anatomical shape of the symphysis; • D: is identified with the center of the symphysis’ inferior part and with the PM point allows a better evaluation of the lower facial height in edentulous or in cases where particular symphysis’ shapes localize the PM too high or too low; • Po-Pogonion: most anterior point of the anterior edge of the symphysis; • ME-Menton: the lowest point of the mandibular symphysis; • AR-Articular: point of intersection between the occipital bone’s base and the posterior part of the mandibular ramus; • X I : geometrically built point, it indicates the center of the mandibular branch. For its construction it is crucial to have as reference the Frankfurt plane, the perpendicular line to it that cuts the PT, and a precise tracing of the ascending ramus’ profile; • DC: Center of the condyle neck on the BA-NA plane; • CF: point of intersection between FH and the perpendicular to FH, passing for PT (pterygoid point) (Fig. 3.17).
Fig. 3.17 Cephalometric points on a LL x-ray of a case of class II, high angle. The red circles indicate the bony points, the green circles indicate the cutaneous points, the blue circles with red outline indicate the main dental points, the green circle with a blue outline indicates the HA hinge axis’ point. Dental points
• • • • •
lower incisor apex; lower incisor incisal edge; upper incisor incisal edge; upper incisor apex; lower canine cusp, vestibular cusp of the first and second lower premolar, mesial and distal vestibular cusps of the lower first and second molar (they identify the occlusal plane and the Spee curve).
These are important for the profile’s aesthetic evaluation: • nose tip; • sub nasal point (this is the skin projection of point A); • most anterior part of the upper lip; • stomion-contact point between the upper and the lower lip; in case of non-competent lips (open bite) the lower and rearmost point of the upper lip and the highest and rearmost point of the lower lip has to be marked; • most anterior part of the lower lip; • skin pogonion: most prominent point of the chin, identified by the tangent going from the nose tip to the chin. Cephalometric plans and lines
• • • •
FH-Frankfurt plane, Pr-OR (Figs. 2.17A-2.17C); axis-orbital plane (Figs. 2.17A-2.17C); A-Po Dental Plane: in Sato’s analysis, the A-B plane is taken; Mandibular plane MP: tangent from the point ME to the lowest point of the mandibular branch; • ANS-PNS: bi-spinal plane; • OP: occlusal plane from the lower incisor incisal edge to the distal-buccal cusp of the lower first molar; • long axis of the upper and lower incisors; • facial plane NA-Po; • aesthetic Ricketts’ plane: from the nose tip tangent to the chin (skin pogonion), the position that the lips take with respect to this line is evaluated; normal value lower lip -2 mm from the aesthetic line; upper lip in contact with the aesthetic line. The values express an aesthetic evaluation of the profile categorizing it as normal, convex, concave. • nose-labial angle: given by the tangent to the lower edge of the nose and the tangent to the upper lip profile; its value is 110° degrees. This angle is very open in cases of II class, second division because of too vertical upper incisors, which are not able to give proper support to the upper lip that appears very thin (Fig. 3.45A). This evaluation is greatly influenced by the shape of the nose, of the chin and, as it will be seen below, by the position of the incisors and by the vertical dimension (Figs. 3.18 to 3.20).
Fig. 3.18 On the tracing we can highlight: • blue, FH plan; • green, axis-orbital plane; • purple, ANS-PNS plan; • yellow, mandibular plane; • red, occlusal plane.
Fig. 3.19 On the tracing we can highlight:
• white, facial plane NA-OP; • red, dental plan A-OP; • yellow, aesthetic Ricketts line.
Fig. 3.20 On the tracing we can highlight: • yellow, upper and lower incisor axes; • red, occlusal plane; • white, A-B dental plane according to Sato.
Tracing on the anterior-posterior The options are a tracing with Cadias® system or using PowerPoint or Keynote to draw vertical and horizontal reference lines and to consider (without calculating the angles) the symmetries’ variation. The tracing made on the radiographic projection in anterior-posterior (Figs. 2.68A-B) allows an assessment of the symmetries-asymmetries on the frontal plane according to the Y-Z axes (vertical dimension and MLD). The main point of reference is the midline that, starting from the apophysis Crista-Galli, passes through: anterior nasal spine, upper and lower dental midline, Menton point (ME). The non-coincidence of the mandibular references (ME, lower dental midline) with this plan allows diagnosing mandibular lateral deviations (MLD). For the purpose of symmetry it is important to evaluate the perpendicularity to the median sagittal plane of the following lines: • orbital zygomatic line: connects the innermost points of the right frontal-zygomatic suture (ZR) and of the left (ZL); • zygomatic line: joining the outermost points of the right zygomatic arch (ZAr) and of left (Zal);
• mastoid line: joins the lower part of the right mastoid process to that of the left mastoid process; • occlusal plane: connects the distal buccal cusp of the right first molar to that of the left first molar; • antegonial line: connects the right antegonial point (AGr) to the left antegonial point (AGl). The vertical dimension is evaluated from the anterior nasal spine (ANS) to menton (ME). This value does not indicate the differences between right and left. These differences are possibly detected by combining the ZL point with the AGl point and the ZR with the AGr; if the heights are different, the mandible will be diverted to the shorter side (Figs. 3.21 to 3.22).
Fig. 3.21 Digital tracing run on the AP x-ray with left MLD: • red, zygomatic orbital line; • blue, zygomatic line; • green, occlusal plane; • yellow, antegonial line.
Fig. 3.22 Tracing on the AP according to Sato: the corners are highlighted in orange for evaluating a MLD of the mandible towards the left side.
Cephalometric analysis It this way, all the necessary information to make the diagnosis and classify the patient from the sagittal, transversal, vertical, dental (incisors) and dynamic points of view (PO, upper incisal tract S1-S2), are disposable.
Vertical analysis The evaluation of the vertical dimension according to Slavicek is called lower facial height; it is defined by the angle formed by Xi-ANS and Xi-PM. According to Slavicek its amplitude is nonstandard, but it is strictly individual and linked to the skeletal structure’s typology of the patient. This measure identifies with the lower third of the face, from the anterior nasal spine to the point PM, on the frontal and lateral view (see Chap. 6, Fig. 6.2 and Fig. 3.23). Fig. 3.23 Lower facial height according to Slavicek.
Fig. 3.23A Angles Xi-ANS and Xi-PM that identify the lower facial height according to Slavicek.
Fig. 3.23B View of the occlusion of the same patient (see Fig. 3.3A for the initial macro-aesthetics of the same patient).
The Cadias® program allows correlating the value obtained to the height of the articulator’s incisal pin, so that to have a reference table on which, for each positive or negative variation of the vertical dimension on the incisal pin, it is possible to reconnect the value of the respective angular variation of the lower facial height. The feedback will be found only if the “zero” point will coincide with the ICP, both on the models mounted on articulator, both for the execution of teleradiographies (see Chap. 2 and Fig. 3.24).
Fig. 3.24 Table of correlation between the vertical dimension in degrees on the cephalometric tracing and its variation in millimeters registered on the articulator’s incisal pin. The blue rectangle highlights the value of the vertical dimension in ICP (43.8°), the zero value of the incisal pin with the models mounted on articulator at ICP and the ideal value of the VD (45.2°). The green rectangle shows that to achieve the ideal VD of 45.2° the articulator’s incisal pin must be lifted of 3 mm starting from the ICP. The red rectangle shows the incisal pin and VD values in the therapeutic reference position (TRP), with a lift of the incisal pin equal to 6 mm, which corresponds to a value of 46.6° of the VD, still remaining within the framework of the standard values (green area on the right of the Gaussian curve).
The resulting value can be displayed on a diagram with Gaussian curve; it will move from a minimum to a maximum (green zone) remaining within a vertical dimension suitable for that specific type of skeletal structure. For functional and aesthetic reasons, if the treatment plan requires it, the vertical dimension can be varied even when its value is normal (in the middle of the curve), since it is possible to move towards an increase or a decrease in VD remaining within the green zone. In fact, statistically, 2 mm of variation on the incisal pin produce an angular variation of 1°. An increase of the vertical dimension of even 6 mm on the incisal pin will produce a variation on the angle width of about 3°, which is almost insignificant, but able to open completely different scenarios to the advantage of the obtained rehabilitative space (Figs. 3.25-3.26).
Fig. 3.25 Digital VTO (DFSD) with the CADIAX ® program (or, better, digital functional smile design of the treatment plan) with variation of 3° of the VD, equivalent to 6 mm on the incisal pin: the new value of 46.6° is greater than to the ideal of 44.4°; but still within the green zone of the gaussian curve.
Fig. 3.26 Final intraoral view with the new therapeutic position, obtained by an increase of the vertical dimension of 6 mm (after 6 years); Fig. 3.3B post-treatment macro aesthetics of the same case.
If the value of the vertical dimension is normal and there is the need to increase it for functional reasons, or to obtain space for rehabilitation, it will be appropriate to evaluate other angles that allow analyzing the vertical dimension more thoroughly. They are: • angle between Frankfurt plan and mandibular plane (FH-MP):allows evaluating the vertical position of the mandible with respect to the skull; value 26°+/- 4° at 9 years old. In the cases in which the lower facial height is correct, but the value of this angle is less than the norm, the VD can be safely varied; • angle between the bispinal plane and the mandibular plane: also this angle frames the lower third of the face, and its value, 24°, is based on the degree of inclination of the upper jaw. If its value is lower than the norm, the same considerations made for the FH-MP angle hold. The upper facial height expresses the value of the upper jaw position and identifies with the middle third of the face (point N point A). The angular value of 53° is given by CF-NA ^ CF-A and is a parameter that will not change with the therapy.
Sagittal analysis’ skeletal class The most used angles to perform the skeletal evaluation are SNA, SNB and their difference ANB: • SNA angle, Sella-Nasion-point A: evaluates the sagittal position of the maxillary bone (the normal value is 80.5°); • SNB angle, Sella-Nasion-point B: evaluate the sagittal position of the mandible (the normal value is 78.3°); • ANB angle, point A-nasion-point B: its value is 2.2° and indicates a class I; larger values represent a class II, lower values indicate a class III; • FH ^ NA-Po, corner of facial depth: (the norm 87°+/-3°) expresses a forward or backward position of the mandible (Fig. 3.27).
Fig. 3.27 SNA and SNB angles (yellow) and facial depth (green) in a case of severe II class with high angle (open).
The cephalometric analysis according to Sato and Kim allows making an immediate assessment of the “skeletal frame” of the lower third of the face based on the skeletal class and on the vertical dimension. This analysis directly correlates the upper jaw fixed part (bispinal plan) to the mandible (mandibular plan), which is the movable part of the system, and to their forward limit given by the dental plan AB. The analysis is primarily based on two angles: ODI (Open Bite Dysplasia Indicator) and APDI (Anterior-Posterior Dysplasia Indicator) (Fig. 3.28).
Fig. 3.28 Skeletal framework of Kim’s analysis given by the triangle formed by the bispinal plane (maxilla), the
mandibular plane (mandible) and the AB plane (dental plane). The APDI is the angle formed by the bispinal plane with the AB plane (green angle, expresses the sagittal position of the mandible). The ODI is the angle formed by the mandibular plane with the AB plane (blue angle, expresses the vertical position of the mandible).
• ODI: according to Sato it is found on the corner formed between the mandibular plane and the A-B plane; it allows framing the skeletal type depending on the vertical dimension (standard value of 72° +/-5°). A higher value indicates a low angle (deep), a lower value indicates a high angle (open); • APDI according to Sato: to be detected on the corner formed between the ANS-PNS bispinal plane and the AB plane (standard value of 81° +/-3°), it allows framing the skeletal typology based on the skeletal class. A higher value indicates a class III, a lower value indicates a class II (Figs. 3.29 to 3.30).
Fig. 3.29 Example of evaluation of a class II. APDI84° (red angle), with high angle variant (open) ODI72° (blue angle).
Sato’s analysis also examines the previously described angles for a further study on VD, such as FH^MP, ANS-PNS^MP and SN^MP, that frame the medium and lower thirds of the face.
Dental analysis: incisors From the cephalometric point of view the upper and lower incisors are evaluated either according to their spatial position with respect to precise points or reference planes, or according to the angles that their long axis forms with specific reference planes (mandibular, bispinal, dental), so that aesthetic and functional aspects can be evaluated. The A-Pogonion dental plan and the closing axis are the main reference planes to evaluate these aspects. The interincisal angle instead, formed by the upper and lower incisors’ long axis, together with the values of over-jet and over-bite, allows evaluating the correlation between upper and lower incisors (Fig. 3.31).
Fig. 3.31 Incisor axes’ relationships with each other and with the dental plane (blue), interincisal angle in green, angle between the upper incisor axis and the dental plane in blue, angle between the lower incisor axis and the dental plane in yellow. From this picture it is clear the importance of the incisors in determining the profile of the soft tissues (white line).
The value of the interincisal angle of 130°+/-6° does not provide information on the inclination of the upper incisor palatal functional surface (S1-S2) and on its inclination related to the SCI, in order to determine the functional parameters. The respect of the incisors’ group cephalometric parameters automatically creates an appropriate support to the lips, which is decisive in the aesthetic construction (Fig. 3.32). Another very important reference from the functional point of view is the angle formed between the closure axis, which goes from the hinge axis to the lower incisor’s incisal edge, and the lower incisor axis; its value is equal to 90°. Fig. 3.32 Incisors’ position in class II.
Fig. 3.32A In the picture on the left, note the relationship between the upper and lower incisors in a case of class II, first division low angle; note the reduction of the interincisal angle and the high values of over-jet and over-bite. In the right picture, a class II, second division high angle, with a large interincisal angle, the absence of over-jet and increased over-bite, also note the appearance of the lips (thin) due to too straight incisors, also set back from the dental plane.
Fig. 3.32B Intraoral view of the left case.
Fig. 3.32C Intraoral view of the right case.
This position of the lower incisor is important in orthodontics, for the dental compensation mechanism. The angle value increases in class III with lingual inclination of the lower incisor and decreases in class II with vestibular inclination (Fig. 3.33). Professor Slavicek’s studies, based on the dynamic functional aspect of incisors, highlight the need to consider, in addition to the incisors’ axis, also the value of the inclination of the upper incisor palatal surface.
Fig. 3.33 On the left picture, the lower incisor’s axis is perpendicular to the closing axis, according to the law of Page (green angle of 90°). The right picture shows the dental compensation mechanism, blue in class III, green in class II.
Carefully looking to an upper incisor, on its mesial or distal profile we can see that the inclination of its axis is different from that of his palatal functional part. To a proper dental axis might correspond a palatal surface too steep or too flat, so the dental axis and its relative interincisal angle are of secondary importance compared to the inclination of the S1-S2 tract (Figs. 3.34 to 3.35).
Fig. 3.34 The picture explains the difference between the dental axis (red line) and the inclination of the upper incisor palatal surface (green line). One can also see that the lower incisor in dynamics, then also the mandible, moves according to the inclination of this surface.
Fig. 3.35 Detail of the dynamic relationship between lower incisor and S1-S2 inclination of the palatal surface of the upper incisor.
In order for the cephalometric tracing to provide in addition to the static picture also the dynamic one, it is necessary to transfer on it the condylography’s dynamic parameters, i.e. the value of the inclination of the articular eminence (SCI). At this point, it is possible to evaluate, by correlating the inclination of the occlusal plane and that of the upper incisor palatal surface to the SCI, if the static design of the incisors’ position is compatible with the functional movements dictated by the articulation (Fig. 3.36).
Fig. 3.36 The picture shows how the inclination of the S1-S2 tract is able to conditioning the mandibular dynamics; also notice the change in position and inclination of the occlusal plane (OP) during the movement.
Dynamic analysis: disclusion angle The masticatory system must perform its functions with the least amount of energy possible, so it is crucial to have the maximum chewing efficiency. The teeth to perform this function must have cuspidate occlusal surfaces; the lower will have to move against the upper teeth maintaining the separation between the two dental arches, with a minimum space and without interference between the teeth. This inter-arch space during functional movements is defined disclusion angle (DA): its value, expressed in degrees, identifies the minimum space between the moving arches so that there is no contact between the teeth, but also avoiding their excessive separation. To derive this important dynamic aspect, the articular eminence’s inclination, the inclination of the occlusal plane and the slope of the tangent to the upper incisor’s palatal surface (divided into S1-S2 tract) have to be correlated to the axis-orbital plane, obtaining angles (Fig. 3.37).
Fig. 3.37 The Viennese trapeze according to Slavicek explains the angular correlation between the axis-orbital plane (green line) and the articular eminence (SCI) green angle, OP (inclination) yellow angle, and S1-S2 tract (inclination) blue angle.
A minimum inter-arch space allows having a good masticatory efficiency with the minimal consumption of energy by the system. A low value (10°) results in a large disclusion with low masticatory efficiency: the ideal value is therefore between 8° and 10°. A good masticatory efficiency is also related to the angle of molars and premolars cusps (CI). The ideal is 30°, but in some cases, with very flat SCI, even 25° may be accepted, so as to avoid an occlusal plane with inclination close to 0° (flat) or even with negative values that give a reverse, so not acceptable, inclination. The disposable values are: SCI (from condylography), CI 30°, ideal DA (8°/10°). The ideal inclination of the individual occlusal plane can thus be derived. This calculation involves the application of the following formula: the eminence inclination (SCI) minus the inclination of the occlusal plane (OP) gives the relative condylar inclination (RCI). The RCI value minus the inclination of the cusps of 30° finally gives the value of the disclusion angle DA (Fig. 3.38).
Fig. 3.38 The picture identifies the angles of the formula to derive the disclusion angle: 1 angle (green) SCI, 2 angle (yellow) of the occlusal plane OP, 3 angle (light purple) of the relative condylar inclination RCI. The angle number 4 shows the relative inclination of the palatal surface of the incisor, which is unnecessary for the calculation.
Formula: SCI – OP = RCI − CI = DA
With a SCI of 45° the ideal occlusal plane must have an angle of 7° degrees to meet the principles of the ideal disclusion angle.
Having established the degree of inclination of the gnathologic OP, this being defined by the lower central incisor and by the distal cusp of the lower first molar, it will be automatically placed in the mandible and any change in the vertical dimension will inevitably cause a change
in its inclination (Fig. 3.39).
Fig. 3.39 The image represents the left mediotrusion in a case of post-orthodontic treatment with MEAW technique; it highlights the minimum entity of disclusion according to the disclusion angle, despite the maximum excursion up to the canine’s edge-to-edge. Of course, the same minimum space is also found on the opposite side.
Again, to individualize the functional parameters, it is necessary a condylographic examination in order to know the SCI. It is necessary to be very careful in attributing mean values (10°) to the OP inclination, because the lack of the individual inclination will have a big impact on the possible presence of occlusal interferences in the posterior sectors of the arch or conversely an excess of separation, which would penalize the masticatory function.
Aesthetics and incisors’ functions The upper and lower incisors have a decisive role from an aesthetic and functional perspective, covering some completely different roles. The upper incisors are part of a fixed system: the maxilla; the lower incisors instead are part of a system, the mandible, which is able to move three-dimensionally, up to interface the upper arch.
Upper incisors It is crucial to frame the functions of the upper incisors. They: • are not used in chewing; • are used in the language; • are modified sensory organs (Sigmund 1870); • enter in interaction with the upper-lower lip and with the tongue; • are referents of an aesthetic function; • influence the mandibular dynamics with their palatal surface (S1-S2). According to Professor Slavicek, what is called incisor guidance is actually an incisor control, as higher and lower incisors are avoiding themselves during chewing. Sigmund, which defines teeth as modified sensory organs, says that they work as proprioceptive sensors. In fact, at the slightest touch, they send out signals that bring back the mandible from the eccentric position
towards the ICP. Their position and shape are critical for the aesthetics, phonation and for supporting the lips. As considered above, the palatal surface of the upper incisors must also comply with precise rules, so that the mandible can move freely (Fig. 3.40). Fig. 3.40 Functional aesthetic characteristics of the incisors.
Fig. 3.40A An aesthetic functional combination of the incisors’ group during the phoneme “V”: the upper incisors are about to reach the boundary line between the vermilion and the oral mucosa of the lower lip.
Fig. 3.40B View from the bottom (6 o’clock) of the same aesthetic and functional characteristics; it is possible to notice the functional space necessary for the mandibular movement in the three spatial dimensions.
Fig. 3.40C Angular view of the S1-S2 tract; the angle of this tract in appropriate relation with SCI automatically creates functionally adequate over-jet and over-bite relationships, and an appropriate positioning of the aesthetic part, which is a consequence of the underlying functional structure.
Fig. 3.40D Inside view of the functional surface: note the functional opening (inclination) that determines the functional space.
The indication of correlating the inclination of the upper incisor’s palatal surface with the SCI, also holds in orthodontics (transversal nature of gnathologic concepts); the torque entered in the attacks or in the wires should take into account the effect which is created on the inclination of the upper incisor’s palatal surface. There is a method to measure the S1-S2 inclination on natural teeth; after the mounting on articulator of the upper model, using an accessory, it is possible to detect a silicone impression of the incisors and canines’ functional surfaces and to measure their angles with respect to the axis-orbital plane. The accessory to be mounted on the articulator has a horizontal part that keeps the parallelism with the articulator’s upper branch, that is to say, with the axis-orbital plane. The abovementioned silicone impression will be cut into thin slices in correspondence with the incisors and canines’ traits to be evaluated (Fig. 3.41). Fig. 3.41 Measurement of the inclination of the upper incisor palatal surface.
Fig. 3.41A Accessory to impress the incisal group (anterior tooth shaper); in this case, it is removed from the silicon to demonstrate the horizontal alignment (axis-orbital plane) and the vertical alignment with the reference axes X and Z.
Fig. 3.41B Cutting of the silicone impression in the functional areas and repositioning of the section on the model to demonstrate that this area can be measured.
The measurement can be manually done by considering the angle formed by the tangent to the incisor palatal surface with horizontal silicone’s part (axis-orbital plane), or digitally by using the Cadias® system after having acquired the image of the cut with references in millimeters. The same manual procedure can also be extended to the teeth of the posterior sector.
Lower incisors As previously mentioned, the lower incisors belong to the mobile part of the system. These dental elements: • work as styles that move against the palatal surface of the upper incisors; • constitute an important mechanism of dental compensation; • highlight the OP anterior point; • are involved in phonation;
• support the lower lip. Not having the lower incisor functional surfaces but only the functional point of active centric, which along with the points of the other lower teeth determines the lower active centric arch, this point corresponds to the incisal edge. It is the anterior part of the gnathologic occlusal plane and its spatial placement is the starting point of our wax-up. Normally, its long axis forms a 90° angle with the closing axis; this angle may increase in class II and decrease in class III, causing the lower incisor to play the important function of dental compensation (Fig. 3.33). In orthodontics, the intervention is on the torque in a crown-vestibular or crown-lingual sense (dental-alveolar compensation). In prosthesis, the praxis is to move the active centric point (incisal edge) toward the vestibule or the tongue (prosthetic hand). So it is crucial to know this position in order to gnathologically guide the tooth’s preparation (Figs. 3.42 to 3.43). Fig. 3.42 Lower incisor compensation mechanisms.
Fig. 3.42A Orthodontic compensation: acts both on the crown and on the root.
Fig. 3.42B Prosthetic Compensation: acts only on the crown. In order to achieve it without causing dental technical problems it should be planned in the treatment plan in order to ensure that the preparations are gnathologically guided.
Fig. 3.43 Schematization of the functional and aesthetic areas of the incisors: green line functional area S1-S2, red line active centric of the lower incisor, white line aesthetic area upper and lower incisor.
Once the spatial coordinates of the lower incisor’s position have been set, it is possible to use the aesthetic canons of dental proportions, golden rules etc. Having established the lower incisor’s height and its compensation’s inclination according to the skeletal class, a specific shape for the anterior part of the active centric arch is produced, therefore a narrower or wider inferior arch. This is reflected on the width of the superior arch and therefore on the size of the teeth. A forward inclination beyond 90° produces an increase of space, i.e. diastemas and the need to increase the medium-distal dimensions of the incisors.
Conversely, an inclination smaller than 90° causes a crowding and the need to decrease the medium-distal dimensions, then to create smaller incisors. Thus, it will be the function to establish the teeth position and their consequent right proportions. After a first waxing of dental volumes it will be up to the technician’s skill to manage the aesthetics according to the functional parameters. Since the functional arches must be coordinated with each other, it is unthinkable to create firstly the perfect shape of upper incisors and canines and then adapt the lower teeth and their function: this would be a high risk compromise. These concepts are equally valid for full dentures, where the choice of the teeth size according to standard parameters related to the nose dimension is not always conjugated with the functional teeth’s setup. In orthodontics, where you have natural teeth with already established dimensions, to maintain these features it is possible to have the opening of diastemas that will have to be closed with direct or indirect additive techniques. It is necessary to avoid closing these spaces with elastic chains because too narrow arches will be created, with the consequent restriction of the mandible and tongue’s functional spaces (Fig. 3.44). Fig. 3.44 Functional space and inclination of the incisors.
Fig. 3.44A Incisor functional position with appropriate functional space.
Fig. 3.44B Management of incisors’ position related to non-functional canons that determines an absence of free functional space, setting the stage for a severe dysfunctional problem and for a therapeutic failure.
Vertical dimension and incisors The therapeutic phase with an adequate management of the VD, related to skeletal and articular parameters, allows creating an anterior group’s shape and aesthetics, which are in harmony with the function and the perioral tissues. A low VD very often causes the lower anterior crowding, flaring of the upper incisor group with opening of diastemas, incorrect lingual posture with problems related to breathing (snoring), mandibular retro-positioning with articular and postural problems. Combining the functional with the anatomical harmony, the best aesthetic result will be automatically reached. In severe collapses of the vertical dimension, the phonetic tests are not sufficient to restore the correct VD without making first an initial pre-treatment with provisional prostheses, so as to positively recondition the system. As already said, the starting point of the treatment cannot be the construction of the upper and lower incisor group, by imposing dogmatic aesthetic canons, sometimes out of context. These canons may not take into account the fact that what will be built on the anterior part will also definitely influence what will be built on the posterior area (i.e. molar area). The extent of the vertical dimension is crucial for handling the correct incisors’ position and consequently that of the lips, that is to say the aesthetics of the lower third of the face. The final aesthetic evaluation can be made only after having obtained a stable TRP, with a readaptation of the stomatognathic system in the new position. Phonetic tests (pronunciation of the S and V letters) performed in a system in which the vertical dimension has not been increased yet, with contracted labial and masticatory muscles, will lead to an underestimated evaluation of the length and position of the incisors. If the vertical dimension is established instead in the initial project considering the skeletal parameters, the incisors will be positioned in accordance with the function. Initially they may seem overly visible, but as the system relaxes, they will integrate very well with the aesthetics of
the face. Indeed, in some cases, following the assessments that will arise from the re-mounting on articulator of the therapeutic provisional, it could be necessary to increase their length, in order to make them visible over the lip profile, always respecting the rules of dental proportions (Fig. 3.45). Fig. 3.45 Dental-labial mini aesthetics subsequent to an orthodontic treatment.
Fig. 3.45A Case of class II division II low angle with concave profile, thin lips, large nasolabial angle and incisors with very open interincisal angle.
Fig. 3.45B Non-extractive orthodontic treatment result with MEAW technique; the functional approach with VD and incisors’ control allowed an excellent recovery of the dental-labial macro- and mini-aesthetics in a functional mandibular position.
The possibility of managing the length of the incisors according to the aesthetic canons of visibility over the lips’ margin depends on the vertical dimension, and then on the posterior support that is necessary to create in order to maintain the distance between the dental arches in ICP. Managing only the length, the aesthetics will be taken into account, but without individually handling the VD, and the result would be a deep bite in the ICP position and an inadequate situation from the functional point of view. The approach based on the management of the functional VD also provides to reduce the need for interventions of clinical crown lengthening (surgical-biological approach) and creates space for the crowns (Figs. 3.46 to 3.47). Fig. 3.46 Proof of the importance of the variation in VD for the functional design of a case with severe destruction of the incisors’ group (same case of Figs. 1.21 to 1.22).
Fig. 3.46A Digital test between functional approach on the right half arch, and biological approach (surgical) with lengthening of the clinical crown on the left half arch.
Fig. 3.46B In ICP, restoring the aesthetic parameters of the incisors’ shape without varying the VD, the initial deep bite, which caused the problem, is reobtained.
Fig. 3.46C View on the model of the possibility of restoring the aesthetic parameters by varying the VD, reconstructing the occlusion in therapeutic position.
Fig. 3.46D View of the designed treatment plan resulting from the wax-up in TRP following the Vienna School’s canons.
Fig. 3.46E Lateral view of the new functional shape of the incisors, to be noted the restoration of the free functional space.
Fig. 3.47 Schematic demonstration of the old position, and shape and position of the incisors (green outline) in the new TRP position.
As previously mentioned, in the presence of a collapse of the VD a deep bite can be highlighted, together with the flaring of the upper incisors with increased axis’ inclination, and the consequent appearance of diastemas, or a crowding of the lower incisors. If the parafunction overlaps to these typical signs, problems may emerge in the supporting tissues with severe destructions borne by tooth enamel. In these situations, thinking only about the dental correction with purely aesthetic purposes, exposes to major risks. It might cause an iatrogenic problem or implement a treatment with high probability of failure, as the compensation that the body puts in place to avoid the impact of the problem on not purely dental districts (muscles, TMJ) will be taken away. In these cases, the rehabilitation on natural teeth or implants (facets, crowns), which usually is realized in the incisor area, prevents the normal compensation, and the abnormal forces that will arise are able to create serious problems both to the prosthetic structures (chipping and fractures of the aesthetic covering) and to the elements of natural or artificial support (unscrewing, abutments fractures, peri-implantitis). When the diagnosis and the subsequent treatment plan are incorrect, the relapse of the orthodontic treatment and the abovementioned problems must be viewed as a defense mechanism of the system against an inappropriate therapy. Therefore, they are an attempt by the body to defend itself by restoring paradoxically more functional, not aesthetic, automatic compensations (crowding, dental rotations, dental abrasion etc), since they tend to undo what is functionally incorrect. In these cases, it can be harmful to implement retention systems with the aim of maintaining the dental alignment or preventing the opening of diastemas because the automatic compensation is hindered, and the onset of dysfunctional problems in other districts cannot be prevented. It is wrong to simplify the solving of the abovementioned problems by acting on the specific problem in a particular area: the diagnosis must always be extended in search of the cause that led to the onset of the problem. Only in this way, a localized therapy can be implemented, accepting compromises on function, which in any case must always guarantee the therapeutic result.
Occlusal plane Introduction From what exposed in the previous chapters, it clearly appears the need to place the teeth in the functional space defined by the VD according to well defined references. The teeth of the two dental arches, upper and lower, must enter in contact with each other, and the plan that identifies the contact of the occlusal surfaces, i.e. the upper and the lower one, is called “occlusal plane” (OP). The occlusal plane is of critical importance as regards its position in the context of the functional space and especially with regard to its inclination. At this point, its exact definition will be necessary in order to identify it, it will be extremely important to establish its exact location with respect to a reference, so it can be positioned spatially and its inclination can also be measured. Clinical evaluation may describe the unsteady shape of the OP because of teeth’s extrusions and inclinations, but never provides precise references, measurable and reproducible, which instead are required by the clinician (Fig. 4.1).
Fig. 4.1 Clinical evaluation of the occlusal plane (frontal view); we can describe the uneven shape and the different inclination of the left and right occlusal planes, but we cannot extrapolate other information that relates to the quantification of inclination and to the placement in the functional space.
The reproducibility of the occlusal plane’s characteristics is important for the diagnosis and for subsequent communication with the dental technician who will handle the reconstruction. The occlusal plane is another determinant of the system that cannot be standardized, but it must always be assessed taking into account the skeletal individuality of the patient and, most of all, the dynamic aspect.
To determine the characteristics of the OP, firstly it is necessary to consider which arch it will be referred to (the upper or the lower), if there is also a relationship between the occlusal plane and the development of the craniofacial system, i.e. whether there is a correlation between the development of a certain skeletal type and the inclination of the occlusal plane. To answer these questions we need to develop an evaluation of the occlusal plane on the LL x-ray of the skull and on the models mounted on the articulator, using as reference the axisorbital plane to quantify the inclination and place it on the lower arch (gnathologic occlusal plane). From Sato’s studies emerges a strong correlation between the development of the maxillofacial system and the inclination of the occlusal plane. The occlusal plane determines the relationship between the two dental arches, therefore it determines the spatial position of the mandible and the consequent macro aesthetics of the face. In turn, the mandible, through its the close connection with the temporal bone, is able to influence the other cranial bones such as the sphenoid, the occipital, the vomer. The correction of the occlusal plane’s inclination becomes crucial in the management of the treatment plan aimed at correcting malocclusion according to the principles of the mandibular repositioning. The sole lateral picture of the dental arches, even if well performed, that is, parallel to the teeth mating line, is not adequate for the evaluation of the occlusal plane because it has not a reproducible reference point. In fact, the inclination and position of the lower OP vary in the moment in which the VD changes; the same can be said with regard to the photographic evaluation of central incisor’s inclination, the upper and the lower one (Figs. 4.2-4.3).
Fig. 4.2 Clinical evaluation of the OP with separated dental arches; two occlusal planes are detected, the upper (green) and the lower (red): which to choose? The lower occlusal plane appears to have a negative inclination with an inverse slope (i.e. posterior inclined). Fig. 4.3 Evaluation of the occlusal plane and inclination of the incisors in three different conditions.
Fig. 4.3A Evaluation on the lateral picture.
Fig. 4.3B Evaluation on models mounted on articulator referred to the axis-orbital plane.
Fig. 4.3C Evaluation of the same parameters on the LL x-ray of the skull, again with reference to the axis-orbital plane. It is evident that from the evaluation of Fig. 4.3A is not possible to conduct an objective diagnosis.
Making use of pictures in order to evaluate the OP can be a simple method, but it does not allow any objective assessment, leading instead to large measurement errors and, consequently, therapeutic errors. On the contrary, the analysis of models mounted on articulator on the axis-orbital plane, supported by a lateral x-ray of the skull on which will be detected and fixed parameters with respect to a reference plane (axis-orbital), will allow using objective, measurable, individual (relative to the patient in question) values, verifiable by everyone and reproducible.
Occlusal plane and craniofacial development Sato’s studies clearly demonstrate the crucial role of the occlusal plane in influencing the maxillofacial development. This must inevitably lead to reconsider which elements are important from the diagnostic point of view to implement a therapy that focuses on the functional aspects and that can ensure long-term stability. During a therapy oriented to the reconstruction of the occlusion, either it is orthodontic or prosthetic, it will thus be determinant focusing the treatment on the causes of the problem. In order to explain how the occlusal plane interacts with the craniofacial development is necessary to consider some cranial bones such as the occipital, the sphenoid, the vomer, the ethmoid, the maxillary and the two temporal (respectively the right and the left) which, with the two temporo-mandibular joints, connect the mandible to the skull (Fig. 4.4).
Fig. 4.4 United and separate view of the cranial bones that will be taken into account to explain the interaction between cranial-facial development and occlusal plane. (Edited by: S. Sato, Master Course Donau Universität Krems)
To explain the craniofacial dynamics it is necessary to take into consideration the growth typologies, in flexion or in extension, of the occipital and of the sphenoid bones with respect to their centers of rotation: these two bones identify the skull base and are articulated to each other through the spheno-occipital synchondrosis. Will precisely be these two growth mechanisms, that of the sphenoid and that of the occiput, to determine the direction of growth of the maxilla. Consequently, the mandible will continuously adapt to the growth of the maxillary bone, therefore to the typology of the maxillary occlusal plane. During the evolution, from a type of growth mostly in extension, therefore with greater development in the sagittal direction, we passed to a growth more in flexion, with a predominance of the development in vertical direction, with respect to the sagittal one (Figs. 1.2-1.3 and Fig. 4.5). The sphenoid rotatory movement is transmitted through the vomer to the maxilla and indirectly to the mandible, which in turn, via the TMJ, acts on the temporal bone (Figs. 4.6-4.7).
Fig. 4.5 Growth in extension in the primate, following evolutionary step with a type of growth in flexion that leads to a craniofacial development in a more vertical than horizontal direction. (Edited by: S. Sato, Master Course DonauUniversität Krems versität)
Fig. 4.6 Connection chain between sphenoid, vomer and maxilla. From the figure it can be imagined how a kind of growth in flexion or in extension of the spheno-occipital complex can act on vomer and through it on the growth direction of the maxilla. (Edited by: S. Sato, Master Course Donau Universität Krems)
Fig. 4.7 Connection mandible-temporal bone through the temporomandibular joint: this is the point of connection between occlusion, thus mandibular position, and cranial bones. (Edited by: S. Sato, Master Course Donau Universität Krems)
The extension or flexion movement is identified at cephalometric level with a variation of the angle of the cranial base, Basion, Sella, Nasion (Ba-S-Na). According to G.D. Hopkin’s studies (1968), the variation of this angle is closely related to the type of skeletal class. Compared to the first class (124°+/-5°) it decreases in III classes (flexion) and increases in II classes (extension). In the sphenoid’s rotation in flexion (the angle Ba-S-Na tends to decrease) the vomer is pushed down and rotates posteriorly. This vomer’s movement pushes the maxilla in a lower position, hindering its growth forward and increasing instead the vertical growth; in this way the length of the maxilla will be reduced, as well as the space in the posterior area of the dental arch, which will decrease creating the conditions for a discrepancy in the posterior sector (Fig. 4.8).
Fig. 4.8 Growth with spheno-occipital rotation in flexion, as shown by the arrows, with a consequent reduction of the skull’s base angle and a “pushing downward” action on the vomer and, subsequently, on the maxilla. (Edited by: S. Sato, Master Course Donau Universität Krems)
In the sphenoid’s rotation in extension the vomer is pushed forward and rotates anteriorly (the angle Ba-S-Na tends to increase). This vomer’s movement pushes the maxilla forward encouraging its growth in length and reducing instead the vertical growth. There will therefore be as a result an increase at the level of the maxillary tuberosity with space for molars and absence of extrusive effect, resulting in less vertical height in the posterior sector. At this point there is not any posterior vertical stimulus for the forward growth of mandible that, being shorter, will create the preconditions for the posterior discrepancy and a mandibular growth in postero-rotation (clockwise) (Fig. 4.9).
Fig. 4.9 Growth with spheno-occipital rotation in extension, as shown by the arrows, with consequent opening (increase) of the skull’s base angle and action of pushing down and forward (more) on the vomer and subsequently on the maxilla in the same direction. (Edited by: S. Sato, Master Course Donau Universität Krems)
In the light of what Sato has studied, it remains difficult to explain the direction of the
maxillary growth forward or downward, and therefore the orientation of its occlusal plane, without taking into account the influence on it of the rotatory movements of the sphenooccipital complex. From the functional point of view, the growth of the mandible is a continuous adaption to the position of the maxillary OP, first through a muscolar adaptation, which is followed by modifications borne by condylar and articular structures, with remodeling or growth (Fig. 4.10). The concept of growth linked to the functional adaptation of the mandible to the maxilla extends beyond the concept of heritability of genetically determined malocclusions. Indeed, the different plans of treatment, from that of interceptive orthodontics to that of orthodontics in permanent dentition, up to complex rehabilitation, will be reviewed and addressed according to the directions underlain in these revolutionary concepts. Fig. 4.10 Growth in extension in a case of Class II high angle and alterations of the condylar anatomy, often associated with this skeletal type.
Fig. 4.10A Growth direction of the maxillary bone down and forward, because of the spheno-occipital extension; a significant discrepancy in the posterior region and the variation of the OP inclination (steep posteriorly) is well visible.
Fig. 4.10B Ortho-panoramic x-rays which highlights the demodelling of condylar surfaces (mostly the right) due to the pressure caused by a growth in extension, with the mandibular posterior rotation (high angle).
Fig. 4.10C Right intraoral view from where the effects of the posterior discrepancy on the eruption of 17 (scissors bite) are evident. Normal growth
The normal growth of the maxillofacial complex is mainly vertical, with a tendency to hyperdivergency. This trend is caused by the hypereruction in the molar area, which creates occlusal interference and mandibular postero-rotation (clockwise). This process requires an occlusal adaptation with an anterior rotation (counterclockwise) of the mandible, movement mediated by the mimic perioral muscles and tended to avoid an open bite (Fig. 4.11). So the maxilla grows downward; consequently its occlusal plane follows the same direction of downward growth, decreasing its inclination. The mandible functionally adapts to the superior OP and rotates anteriorly and forward decreasing the inclination of the mandibular plane (MP): all that favors a secondary appositional condylar growth, with stabilization of the mandibular position in the functional space (Fig. 4.12).
Fig. 4.11 Mandible growth with a tendency to hyperdivergency and to posterior rotation due to the pre-contact in the molar area (red arrow). Anterior rotation’s reset through the anterior mimic muscles (dotted mandibular shape). (Edited by: S. Sato, Master Course Donau Universität Krems) Fig. 4.12 Normal cranial-facial development
Fig. 4.12A The figure shows the lowering of the upper OP, due to the downward growth of the upper jaw (PP) and the relative lowering of the mandibular plane (MP) due to the mandibular anterior rotation. Indeed the mandible searches for occlusal mating with the upper jaw and all this leads to a secondary condylar growth (red zone on the condyle head). (Edited by: S. Sato, Master Course Donau Universität Krems)
Fig. 4.12B Following the mandibular anterior adaptation the symphysis moves anteriorly bringing to the progression of point B, resulting in the increase of the angle between AB and PP (APDI) and of the angle MP-AB (ODI); these changes highlight the growth in anterior rotation of the mandible. One can also note how this adaptation is able to maintain a balance between lowering of the occlusal plane and mandibular anterior rotation. (Edited by: S. Sato, Master Course Donau Universität Krems)
The E. Richardson’s studies show that during growth between 6 and 16 years, there is a reduction of the angle between OP and FH as well as a reduction of the angle between FH and MP, confirming the anterior mandibular rotation to adapt to the angle’s change of the upper OP (flattening). The same evidence was demonstrated by Sato, who has detected an increase in the angle APDI, which quantifies the anterior-posterior position of the mandible (see Chap. 3). This concept of OP flattening and anterior mandibular rotation, as will be described later, is the keystone of the mandibular repositioning based on the management of the occlusal plane’s inclination (OMRT technique). Development of a class II
Excessive growth in extension at the spheno-occipital level induces the development of a class II facial typology, according to the following process: • spheno-occipital extension; • vomer’s growth forward; • antero-rotation of the maxilla; • absence of posterior-superior discrepancy due to a wider maxilla; • low vertical dimension in the posterior sector, in view of the lack of molar hyperestrusion; • steep posterior occlusal plane; • inhibition of mandible’s forward growth which will be undeveloped and posteriorly rotated, with strong posterior-inferior discrepancy; • condylar compression and inhibition of its growth by apposition, because of the posterior mandibular rotation; • internal rotation of the temporal bone as a consequence of the induced effects on the
mandible. Therefore, in a class II you will have a growth in extension, with posterior mandibular rotation, posterior-inferior discrepancy, hypereruption of lower molars and consequent steep posterior occlusal plane (Figs. 4.13 to 4.15).
Fig. 4.13 Summary of craniofacial development in extension in a class II typology. (Edited by: S. Sato, Master Course Donau Universität Krems) Fig. 4.14 Development of a class II open bite.
Fig. 4.14A Teleradiography showing the growth in extension and the failure of the mandible to adapt in anterior rotation (open bite), with condylar compression (anterior superior). Evident discrepancy in the posterior sector and excessive inclination of the posterior OP.
Fig. 4.14B The ortho-panoramic exam shows the condylar demodelling; also evident are the posterior discrepancy and the effects linked to it with hyperestrusion of the mandibular posterior sectors and steepening of the posterior occlusal plane. Fig. 4.15 Dental arches’ view of the relation between dental class and OP inclination.
Fig. 4.15A Evaluation of the difference in inclination between gnathological OP (red) and posterior OP (green) on the models mounted on articulator.
Fig. 4.15B The intraoral vision is not able to highlight the real situation concerning the inclination and the position of the OP. Development of a class III
Excessive growth in flexion at the spheno-occipital level involves the development of a class
III facial typology. This abnormal development will follow, unlike the class II, this process: • spheno-occipital flexion; • vomer’s growth downward; • downward growth of the maxilla; • posterior-superior discrepancy due to the shorter maxilla; • vertical dimension increased in the posterior region in view of upper molars’ hyperestrusion; • flat posterior occlusal plane; • forward growth of the mandible with its anterior rotation; • condylar decompression with increased secondary condylar growth by apposition, because of the anterior mandibular rotation; • external rotation of the temporal bone as a consequence of the induced effects on the mandible. So in a class III there will be an increase in flexion with anterior mandibular rotation, posterior-superior discrepancy, hypereruption of the upper molars and consequently a flat posterior occlusal plane (Figs. 4.16 to 4.17).
Fig. 4.16 Diagram of craniofacial development in flexion in class III typology. (Edited by: S. Sato, Master Course Donau Universität Krems) Fig. 4.17 Development of a class III.
Fig. 4.17A Teleradiography showing the growth in flexion, with large predominance of the vertical component; mandibular adaptation resulting in anterior rotation with condylar decompression. Evident discrepancy in the posterior-superior sector with decreased inclination of the posterior OP.
Fig. 4.17B The ortho-panoramic examination shows normal condylar growth; also evident are the posterior discrepancy and the effects linked to it with hyperestrusion of the maxillary posterior region and flattening of the posterior occlusal plane. Early germectomy of the lower third molars, eliminating the inferior discrepancy, prevented a further increase of the trend to the anterior open bite.
Fig. 4.17C Evaluation on articulated models of the difference (minimum) of inclination between the gnathological OP (red) and the posterior OP (green).
Fig. 4.17D The only intraoral vision is not able to point out the real situation regarding the OP inclination and position with respect to what can be inferred instead from articulated models.
In conclusion, a class II will be characterized by a steep occlusal plane, while a class III by a flat occlusal plane. A posteriorly rotated (in a class II) or an anteriorly rotated (in a class III) mandibular position will correspond to the different types of OP: this highlights the interdependence between the occlusal plane’s inclination and the mandibular position. The treatment based on mandibular repositioning should be directed to the correction of the occlusal plane’s inclination as integral part of the treatment plan, whether orthodontic or prosthetic. If a steep OP creates a class II, for its correction it will be necessary to decrease the inclination favoring an anterior rotation of the mandible, with consequent articular adaptation (Fig. 4.18). A flat OP determines the onset of a class III: for its correction it will be necessary to increase the inclination in order to favor a posterior mandibular rotation, with consequent articular adaptation (Fig. 4.19).
Fig. 4.18 In the class II correction the OP flattening (thick red line) favors the anterior repositioning of the mandible, using the joint adaptation (joint compensation).
Fig. 4.19 For the correction of a class III, the OP steepening (thick red line) and the vertical compensation management favors the posterior repositioning of the mandible, resulting in joint compensation. Development of a mandibular lateral deviation
If there is a difference in growth between the left and the right side of the dental arches, a mandibular lateral deviation will be developed (MLD). The side with molar hypereruption will increase the vertical dimension: consequently the mandible will rotate to the opposite side. The condyle, from the side of the shift, will go into compression with growth inhibition. On the opposite side, the pressure unload will favor a growth by secondary apposition: naturally, two different occlusal planes will be stabilized, one steeper on the side of the deviation, the other flat on the opposite side. The development of this malocclusion is closely linked to posterior discrepancy. From the side where the posterior discrepancy is small the molar teeth will erupt earlier, producing an
increase in vertical dimension, which will result in a flat occlusal plane. The mandible will be induced to deviate towards the opposite side, where the vertical dimension is lower, because of the molars’ eruption delay caused by the higher posterior discrepancy. Sato and Tamaki’s studies have shown that in order to correct this type of malocclusion it is necessary to act on the occlusal plane and on the posterior support, which should be increased from the side of the deviation so that the mandible can reposition itself to the center (Fig. 4.20). Fig. 4.20 Development of a mandibular lateral deviation to the left side.
Fig. 4.20A Same patient of Fig. 4.10: on the AP radiography it is well-visible how the VD increase on the right side caused a MLD on the left side, where the VD is lower; the cause lies in the wide posterior discrepancy.
Fig. 4.20B The blue arrow indicates the increase of the right vertical dimension with left MLD. The right condyle, unloaded, will grow by apposition; the left one will face a demodelling because of pressure, setting the stage for a future dysfunctional problem.
Posterior discrepancy concept according to Sato In the past, orthodontists have set the therapy, and they still do today, mostly on the concept of anterior discrepancy. In this way, with the area going from the anterior arch to the first molars as reference, they conduct an evaluation based on the difference between dental diameter and dental arches’ width. To create more space in the anterior sector extractive therapies are used therefore, especially those regarding the first premolars. These treatments do not solve the problem, exposing instead to relapses and dysfunctional problems. In contrast to this approach that could be called “traditional” and that is generally used, the clinician’s focus should instead move to the posterior sector of the two dental arches, in the 6th-7th-8th area (Fig. 4.21).
Fig. 4.21 Subdivision diagram of the dental arches according to the Sato’s anterior and posterior discrepancy concept.
The presence of the third molar’s germ already dimensionally structured in the coronal volume, at an age in which the arches are not developed yet, leads to what Sato called posterior discrepancy. The effect of the discrepancy results in a dental crowding of the molar area, which causes the teeth’s hypereruption as a result of the squeezing-out effect generated by the lack of space. What Sato called “squeezing-out effect” acts on the inclination of the occlusal plane and leads to the development of the different skeletal types (I, II, III), including their variants in MLD when this effect occurs just on one side (Figs. 4.22 to 4.23).
Fig. 4.22 Effect of posterior discrepancy with squeezing out effect which causes posterior hyperestrusion and teeth’s mesial inclination. Fig. 4.23 8-years-old patient: posterior discrepancy’s signs are already visible.
Fig. 4.23A The ortho-panoramic x-rays highlight very well the large posterior and inferior discrepancy with a big interference of the third molar’s lower germ (just calcified) on the second molar’s eruption.
Fig. 4.23B The LL x-ray of the skull shows the posterior discrepancy’s effect on the posterior mandibular rotation.
Fig. 4.23C Posterior-anterior skull’s teleradiography, which highlights very well the high and external position of the inferior third molar’s germ. It is already visible a MLD to the left side for hyperestrusion to the right side. The xray images give very well the idea of the high and vestibular position of the inferior third molar’s germ; this makes it easily attackable from the surgical point of view, without having to take big risks.
The third molar’s germ pushes up the second molar which in turn pushes the first molar, creating an hypereruption that, if dependent from the lower arch, will lead to a steep occlusal plane, thus to a class II. Conversely, if the same process occurs involving the maxilla, it will lead to a flat occlusal plane, and to a class III (Fig. 4.17B).
Third molars’ germectomy The early germectomy of third molars, especially of the lower third molars, is crucial in the early treatment of class II, as determinant for the control of the occlusal plane’s inclination and as it promotes in this way the anterior adaptation of the mandible. This early intervention is required to control the vertical dimension in the posterior area of the dental arches. It will be desirable to implement the upper third molar’s germectomy at older ages, when the germ will come in a more surgically attackable position, without running major risks; in fact, in the large discrepancies the upper third molar is very high and it would be difficult and risky to proceed with an early germectomy. In particularly severe cases, like those of class III open bite with large posterior-superior discrepancy, it is possible to opt, in the presence of an third molar’s well-structured germ, for the extraction or germectomy of the upper second molar. In this way, by eliminating the posterior-superior discrepancy, the third molar gradually take the place of the second molar. Sato’s clinical evidence confirms this approach: after removing the discrepancy, the space that allows the upper third molar to develop with a normal coronal and radicular anatomy is created, as opposed to what happens in the case of crowding. With early germectomy, when the first calcifications of the crown appear or even before their appearance, the germ of the lower third molar is easily attackable because it is in a high and external position (Figs. 4.23 to 4.25). Fig. 4.24 Anterior discrepancy’s treatment with first premolars’ extraction.
Fig. 4.24A Ortho-panoramic radiography that detects how the classic treatment of crowding, approached from the point of view of the anterior discrepancy with the first premolars’ extraction, has not solved the problem of lack of space as the real cause, that is, posterior discrepancy, has not been considered.
Fig. 4.24B View of the posterior discrepancy permanence on the LL radiography; notice the collapse of the bite due to the decrease of posterior support following the extraction of the first premolars (note also the negative effects of this procedure on the aesthetic profile). Fig. 4.25 Lower third molars’ germectomy.
Fig. 4.25A 9 years-old patient during interceptive orthodontic therapy; an orthopanoramic x-ray is performed to check the posterior discrepancy that is very evident; then the germectomy of #48 - #38 teeth will be made.
Fig. 4.25B Surgical breakthrough for extraction of #38 with envelope flap without vertical incisions.
Fig. 4.25C Suture of the flap.
Fig. 4.25D Germ of #38 that presents only the calcification of the crown, separate, in this case, into two parts; in some cases the crown will be sectioned into four parts, so you can keep a minimum access osteotomy.
This intervention, in addition to be non-invasive, will remove the negative effects on the maxillo-facial development, will avoid the presence of a partially or totally impacted tooth, and will eliminate the risks related to a third molar extraction in adulthood, given the proximity or contiguity of its roots to the inferior alveolar nerve (Figs. 4.26 to 4.27).
Fig. 4.26 Interceptive post-treatment teleradiography and posterior discrepancy’s elimination. Notice the effect of the lower third molar elimination on the OP and on the VD. The upper third molars will be extracted as soon as their position will be lower, in any case before their eruption. Fig. 4.27 Effects of failure in controlling the posterior discrepancy.
Fig. 4.27A 18-year-old patient’s ortho-panoramic x-ray already orthodontically treated, without success. All the problems linked to the non-treatment of the posterior discrepancy are present, aggravated in quadrant two by the presence of a #29. The contiguity of the roots of #48 and #38 with the inferior alveolar nerve clarifies the importance of early intervention, also to avert all the risks related to adult surgery.
Fig. 4.27B Intraoral view of orthodontic treatment’s relapse with left MLD and severe alteration of the occlusal plane.
Occlusal plans There are different occlusal planes and these can be placed either in the upper or in the lower arch, both in the anterior and in the posterior area of the arches. The gnathological occlusal plane according to Slavicek, as mentioned above, is the main reference and is placed on the mandible; it goes from the lower incisor edge to the distal cusp of the lower first molar (third vestibular cusp): its inclination is measured in relation to the axis-orbital plane (Fig. 4.28). Very important for the functional evaluation are the occlusal plans of the upper arch, Upper Occlusal Plane (UOP), described by Sato, especially the superior-posterior OP. They are listed here: • Upper Anterior Occlusal Plane (UAOP), which goes from the central incisor’s edge to the premolars; • Upper Conventional Occlusal Plane (UCOP), which goes from the upper incisor incisal edge to the palatal mesial cusp of the upper first molar; • Upper Posterior Occlusal Plane (UPOP); his excessive steepness is one of the causes of the class II. It is given by the occlusal plane of the first and second molar (Figs. 4.29-4.30).
Fig. 4.28 Gnathological occlusal plane according to Slavicek. It is defined by two posterior points: that of the distal cusp (small) of the right first molar and that of the left, and by an anterior third point, i.e. the incisal edge of the lower incisor taken on mesial part (a plane of triangular shape is then obtained).
Fig. 4.29 In the lower part: the gnathological occlusal plane associated with the mandible; in the upper part: the three occlusal planes associated to the maxilla, UAOP (blue), UCOP (red), UPOP (green). Fig. 4.30 Upper occlusal planes, UOP.
Fig. 4.30A Upper conventional occlusal plane (incisor-first molar; UCOP).
Fig. 4.30B Upper posterior occlusal plane (UPOP).
Fig. 4.30C Upper anterior occlusal plane (UAOP).
Correlation between OP and TMJ Placing as a premise that the occlusal plane has to be flattened in the correction of a class II and made steeper in the correction of a class III, it must be said that the value of its inclination must be correlated with the eminence’s inclination (SCI) and never arbitrarily chosen. As described in chapter 3, this will allow the respect of the disclusion angle’s rule
Fig. 4.31 The accessory for the construction of the OP (Occlusal Plane Measuring) to be used with the articulator allows personalizing the OP inclination correlating it to the SCI, in compliance with the disclusion angle’s rules.
The determination of an individual OP inclination compatible with the SCI becomes crucial when switching from the static position to the functional and parafunctional dynamic movements. On articulator, if the inclination of the occlusal plane is kept fixed (for example at 10°) and the SCI is varied, different levels of arches’ separation (i.e.disclusion angle) will be obtained, going from an excess of space to the presence of posterior interferences. The same thing happens if, keeping fixed the SCI, the inclination of the OP varies (e.g. too flat or too steep). The posterior interferences will create in the dynamics avoidance patterns that will force the muscular system to work harder, or even bring to an involvement of muscles that do not normally come into action in that specific function. The interferences are created because there is not compliance with the DA; they cause a wrong and incorrect position of mandibular movements, causing therefore a dysfunction of the cranio-mandibular system. In the event that there is a too steep or too flat SCI, in order to respect the disclusion angle, the OP may be too steep or too flat. To overcome this problem, once the ideal angle of the OP is fixed, one can act on the inclination of each molars and premolars’ occlusal surfaces, changing the inclination of their axis (Fig. 4.32).
Fig. 4.32 Occlusal plan management of single teeth: • at the top, the single teeth’s OP (yellow line) corresponds to the gnathological OP (red line): to this corresponds a certain dental axis’ inclination (blue line); • in the middle, the single teeth’s OP is less inclined than the gnathological OP: the dental axis straightens; • at the bottom, the single teeth’s OP is more inclined than the gnathological OP: the dental axis increases its inclination. Compensation mechanisms
At the end of the growth process, the stabilization of a specific skeletal class (I, II, III) will be achieved, with the relative occlusal plane. In order for the cranio-mandibular system to be in functional harmony, the body puts in place compensation mechanisms of the vertical type, dento-alveolar and articular. These same mechanisms can be put in place by the clinician in the treatment plan. In particular, the articular compensation is the conceptual basis of the mandibular repositioning. In prosthetic rehabilitations, the clinician can insert a compensation that will be told prosthetic. Without changing the position of the tooth root (which is possible in orthodontics), with a gnathologically guided tooth preparation, the position of the prosthetic crown can be changed by inserting the compensation needed through the variation of its inclination (see Fig. 3.42 and Figs. 4.33 to 4.34).
Fig. 4.33 Compensation mechanisms put in place by the system at the end of growth: to the left, vertical compensation, in the center, dental alveolar compensation, to the right, joint compensation. (Edited by: Sato-
Fig. 4.34 Prosthetic compensation: in prosthesis, once the TRP is established, the crown’s axis can be changed gnatologically guiding stumps’ preparations. The picture shows a class II case; the crowns of the upper incisors have a palatal inclination, those of the lower incisors have a vestibular inclination, to compensate for the excessive over-jet.
Occlusal concepts Introduction In the previous chapter, the development of the maxillofacial complex has been examined, based on the spheno-occipital extension and flexion mechanisms and on the posterior discrepancy. Also the effects that these processes produce on the occlusal plane have been taken into account, determining the development of different skeletal types, with different occlusal relation between the teeth of the upper and lower arches. The definition of the occlusal relation, as already said, is the result of a continuous functional and structural adaptation of the mandible to the shape of the maxillary arch (position and inclination of the incisor group). According to Angle, the ideal dental class relationship is class I, which is therefore the reference in implementing the eventual occlusal relations’ corrections. During the growing period the eruption of the first milk teeth, that is of the incisors, first the lower then the upper, is responsible for the first functional interferences to the mandible’s protrusive movement. The stomatognathic system reacts to these interferences with a continuous, slow, firstly muscular then structural adaptation of the TMJ. In fact, the body tends to put in place compensation mechanisms, so as to reach a “eufunction”, also in case of dysgnathias. Thanks to the adequate knowledge of functional concepts, although it is not possible to act on the shape of the teeth, early intervention will be implemented by amending their position in space. In fact, a functional orientation of the occlusal surface (cusps, fossae, marginal ridges and so on…) will restore the right functions orienting the system towards the eufunction, favored by a muscular adaptation that determines permanent structural changes. This chapter will present the path of the ontogenetic development of the occlusion, from the post-natal period to the adulthood’s complete dentition. In addition, it will highlight the need for interceptive therapeutic intervention that aims to correct any occlusal abnormalities (deep bite, cross bite), before they produce changes of the stomatognathic system at the structural level (e.g. asymmetry). Summing up, the need for an accurate knowledge of the occlusal gear will be underlined again in order to ensure, by means of the clinician’s targeted interventions, an adequate development of dental class I. Occlusal concepts will be defined, enabling the achievement and maintenance of normal function and underlining their importance for application in therapy. Finally, the functions of the various dental groups (incisors, canines, premolars, molars) will be analyzed, clarifying what has to be their position on the dental arches, on well-defined functional arches, which will allow the right dynamic.
The anatomy of dental crowns is already fully structured before their eruption in the oral cavity; it can change only for destruction, as a result of functional wear or because of parafunction (see Figs. 1.15B-1.21 and Fig. 5.1). The occlusal surface of the first permanent molar (Figs. 5.1B and 5.27A) and the palatal surface of the upper central incisor are very pronounced anatomies with unique features, which mark a clear passage from the abraded or poorly defined anatomy of the milk teeth to that typical of permanent teeth (Fig. 5.1C). Fig. 5.1 Patient in the first period of the mixed dentition.
Fig. 5.1A Ortho-panoramic x-ray of a patient in mixed dentition: it highlights the fact that the crowns of the permanent teeth are already fully structured, for what concerns shape and size, before their eruption.
Fig. 5.1B Upper arch of the same patient; notice the unique anatomical features of the upper first molar and of the upper central incisor.
Fig. 5.1C Details of shape and inclination of the palatal surfaces of the upper incisors.
In the development of dentition, we can distinguish three stages: milk dentition (deciduous), mixed dentition (deciduous and permanent), permanent dentition (Fig. 5.2). Fig. 5.2 Upper arch during the three main phases of ontogenetic development.
Fig. 5.2A Milk dentition.
Fig. 5.2B Mixed dentition.
Fig. 5.2C Permanent dentition.
Given that the masticatory organ develops according to its functions (Chap. 3 Fig. 3.1 and 3.2), during the various developmental periods the growth path must be understood as a continuous adaptation to the functions, to the various teeth forms and to their positions in the arches. From the milk to the permanent dentition it is possible to distinguish the following functional developmental periods: • post-natal period; • milk teeth development period; • full milk dentition period; • first stage of mixed dentition; • second stage of mixed dentition; • permanent mature dentition period. Postnatal period
At this stage there are no teeth and the main functions are: breathing, breast or bottle feeding and a primitive verbal communication. For what concerns the mandible, the vertical development of the ascending ramus is almost absent while the horizontal component of the mandible’s body is dominant; the occlusal plane and the TMJ are flat. The TMJ at this stage is therefore flat and the main movements are protrusion and retrusion, so as to perform the milking effect, the base of the breast feeding’s mechanism (Fig. 5.3). Fig. 5.3 Post-natal period and early development of milk dentition.
Fig. 5.3A Appearance of lower incisors at around six months-old.
Fig. 5.3B Skeletal situation: notice the predominance of the horizontal component of the mandibular body (green line) compared to the vertical (yellow line) and the parallelism between TMJ inclination and OP (at this stage they are flat). (Edited by: S. Sato, Master Course Donau Universität Krems) Milk teeth development period
At about 6 months, the milk incisors, upper and lower, erupt: they cause the first functional interferences to the mandible’s protrusive movement, causing a narrowing of the motion’s range (Fig. 5.3A). This in turn causes the initial muscular functional adaptation with a consequent TMJ’s structural modification: the joint starts to be modeled accordingly (Fig. 5.4). Fig. 5.4 Milk dentitiom development’s phase.
Fig. 5.4A Upper arch during the eruption of milk canines (C): the milk little molar (E) is not erupted yet, to completion of the deciduous dentition.
Fig. 5.4B Lower arch during the eruption of milk canines (C): the milk little molar (E) is not erupted yet, to completion of the deciduous dentition.
Fig. 5.4C Upper arch of the patient in which have erupted the milk little molars (E).
Fig. 5.4D Skeletal situation: notice the growth of the mandibular vertical component (yellow line) and a certain inclination of the TMJ and of the OP. (Edited by: S. Sato, Master Course Donau Universität Krems) Full milk dentition period
At two and a half years-old the milk dentition is complete. The main functions of the masticatory organ at this stage are: the chewing, the speech and the swallowing. After this stage, the parafunction “bruxism” may appear that, at this age, you can frame as a physiological mechanism of psychological transfer against prohibitions and obligations imposed by the adults. The resulting abrasion of the occlusal surfaces favors the mandibular protrusion and the appearance of a vertical plane distal to the milk little molars (E), which facilitates the next establishment of a class I relationship between the first permanent molars. Studies carried out by Araya (1973) show that 100% of the distal steps evolve towards a Class II dental relationship (Fig. 5.5). Before the transition to the next phase (around 4.5-5 years), any occlusion anomaly must be detected and corrected; the reference here is for example to: cross bite, deep bite, tendencies towards the development of classes II or III. In this way the stabilization of pathological structural adaptations, due to the fact that the system seeks for the eufunction as far as possible also in the presence of malocclusions, is avoided. The early interceptive intervention allows exploiting this trend and implementing a therapeutic action able to adapt the growing system to the therapeutic correction (Fig. 5.6). In other occasions, the therapy consists in an early elimination of harmful habits such as soothers, in order to ensure that the system spontaneously recovers the eufunction (Fig. 5.7). Fig. 5.5 Distal plan and dental class relationship.
Fig. 5.5A Distal plan to milk molars (E): the green line indicates the conditions (right plan) for the establishment of a relationship of I class among the first permanent molars; the distal step (distal red lines on the lower little molar) indicates the preliminary conditions for the onset of a class II relationship; the mesial step (mesial red lines on the lower little molar) indicates the conditions for the establishment of a class III relationship. (Edited by: S. Sato, Master Course Donau Universität Krems)
Fig. 5.5B The straight distal plan predisposes to an intercuspation of the first molar with a class I relationship.
Fig. 5.5C The plan with distal step prepares to an intercuspation of the first molar with a class II relationship.
Fig. 5.5D The plan with mesial step prepares to an intercuspation of the first molar with class III relationship (note the anterior cross-bite).
Fig. 5.5E Diagram according to Arya (1973) that shows how, depending on the type of the step that is formed between the upper and the lower milk molars (E), the three dental class relationships can evolve in percentages. (Edited by: S. Sato, Master Course Donau Universität Krems) Fig. 5.6 Interceptive orthodontic therapy in a case of cross bite.
Fig. 5.6A Right cross bite with a mandibular lateral deviation to the right side: this is a clear sign of the beginning of the stabilization of a serious asymmetry (in an initial stage of mixed dentition).
Fig. 5.6B The therapeutic approach with the rapid expansion of the palate allows the jaw to recenter, in order to favor the eruption of the first molar in the normal position avoiding the stabilization of asymmetry. Fig. 5.7 Full milk dentition period.
Fig. 5.7A Frontal view of the dental arches with complete milk dentition (2.5-3 years-old): there is an anterior open bite, caused by the soother.
Fig. 5.7B-C Dental arches in the stage of full milk dentition: the presence of a final straight plan without step is a great starting point because the first permanent molar erupts in class I. Note the closing of the bite, which is an automatic consequence once the mechanical action of the soother has been removed.
Fig. 5.7D Facial macro aesthetics at 6 years old in mature milk dentition, before the beginning of the mixed dentition phase.
Fig. 5.7E Skeletal situation: the growth of the vertical component (yellow line) and the increase in the inclination of the TMJ and of the OP continue. (Edited by: S. Sato, Master Course Donau Universität Krems) First stage of mixed dentition
Around six years old, the change of the incisal sector begins, together with the eruption of the first permanent molar, behind the milk little molar (E). The particular anatomy of the occlusal surface of the first molars and the concavity of the
palatal surface of the upper incisors, insert further functional interference, with a consequent muscular (before) and structural (after) adaptation (Fig. 5.8). Fig. 5.8 Upper and lower jaw at the beginning of mixed dentition.
Fig. 5.8A Right intraoral view.
Fig. 5.8B Left view: this being the case illustrated by figures 5.3, 5.4, 5.7, notice how the first permanent molars are reaching a class I relationship. Also note the tendency to the stabilization of a deep bite.
Fig. 5.8C Skeletal situation: with the appearance of the first permanent molars and of the incisors the delineation of the permanent dentition’s OP inclination begins. (Edited by: S. Sato, Master Course Donau Universität Krems)
The upper incisors further restrict the limit of the protrusive movement of the mandible (protrusive control) and the vestibular cusps of the upper first molar as well restrict the limit of the laterotrusive movement (laterotrusive control); through the transverse ridge (which combines the distal-buccal cusp to the mesiopalatal one), a control on the mandibular retrusion is also implemented (Fig. 5.27). The maxillary lateral incisor, when It erups, is involved as well in laterotrusive control along with the upper first molar; this function is maintained for a long period, at least until the eruption of the first upper premolars (Figs. 5.9-5.10). Fig. 5.9 Upper arch with eruption of central incisors and of the first molar.
Fig. 5.9A Occlusal anatomy of the upper first molar: the yellow line indicates the retrusive control given by the enamel ridge that connects the mesiopalatal cusp to the distal-vestibular cusp. The green line indicates the first laterotrusive control over the mesio-vestibular cusp.
Fig. 5.9B Anterior functional limit of the mandible: given by the anatomical shape of the upper incisors and by their position, with a high value of the interincisal angle and a tendency to deep bite.
Fig. 5.9C Early elimination of the deep bite with the composite overlay technique (EMRT) that allow, at an early age, to act on the vertical dimension by changing the growth direction of the maxillo-mandibular complex. Fig. 5.10 End of the first phase of mixed dentition.
Fig. 5.10A It can be seen as an early targeted intervention has solved the problem of a mandibular growth tending to a deep bite and to an anterior rotation, and has favored the stabilization of a molar class I relationship, which is essential for the future occlusal stability.
Fig. 5.10B Facial macro aesthetics linked to an early management of the vertical dimension, therefore of the mandibular position. Second stage of mixed dentition
In this phase, the eruption of the first upper premolar, because of the steepness of its buccal cusps, assumes the dominance in laterotrusive control alongside with the incisors, releasing
from this task the molar. The first upper premolar intervenes in retrusive control in cases of the class I along with the first lower premolar, and favors the stabilization of class I intercuspation (Fig. 5.11). Fig. 5.11 Second phase of mixed dentition.
Fig. 5.11A Upper arch with eruption of the first premolar and early eruption of the canines: notice the mesial stripping to milk little molars (E) to create space and thus to favor an ideal intercuspation between the first upper and lower premolars. The dotted green line on the first premolar indicates the laterotrusive control that will create the first molar disclusion. The yellow line on the first upper molar always highlights the retrusive control that stabilizes the anterior position of the mandible.
Fig. 5.11B Skeletal situation: at this stage the molar class I relationship through the retrusive control made by the first upper molar favors the future intercuspation of premolars and canines. (Edited by: S. Sato, Master Course Donau Universität Krems)
Even in classes II the first upper premolar exercises a retrusive control, between the mesial side of its palatal cusp and the distal side of the lower canine’s cusp (Fig. 5.12). Fig. 5.12 Role of the first upper premolar in the retrusive control of classes II.
Fig. 5.12A Evidence of the relationship between the mesial slope of the palatal cusp of the upper first premolar and the distal slope of the lower canine cusp.
Fig. 5.12B Evidence of disclusion in the posterior sector during retrusive movement, mediated by this function.
Fig. 5.13 Upper and lower dental arches in the stage of eruption of the second premolar. Intercuspation in class I of first and second premolars, once the molar class I is stabilized; the situation is favored by an interceptive orthodontic treatment.
Given the crucial role of the upper and lower first premolar, the extraction of these elements for orthodontic purposes in cases of lack of space must be avoided, also considering the posterior discrepancy concept. In this phase also the second upper and lower premolar erupts, thus the laterotrusive control becomes mesial and steeper with respect to the first molar. Again, from an interceptive point of view, at this stage small mesial strippings to the upper or lower milk little molars are necessary for a correct spatial positioning of the first premolars, in order to promote an intercuspation in class I (Fig. 5.11A). Even the TMJ, at this stage, is almost entirely structured, as regards both its inclination (sagittal parameter SCI) and the transverse parameters (Bennett) (Fig. 5.14). Fig. 5.14 Intercuspation in class I in the premolar area.
Fig. 5.14A Stabilization of the ideal relationship between the first premolars (upper and lower) with the stabilization of the anterior position of the mandible given by the protrusive control that has been created.
Fig. 5.14B In some cases to favor this intercuspation is useful to insert composite artificial guides, such as inclined plane, on the distal part of the upper first premolar.
Fig. 5.14C Intercuspation of the first premolar mediated by the artificial guide. Permanent mature dentition period
The last tooth to change is the canine. The eruption of the permanent canine completes the anterior arch and with the steepness of its palatal surface it assumes the dominance on laterotrusive control, disclosing the area distal to it in the natural respect of the sequential occlusion principles with canine dominance, according to Slavicek (Fig. 5.15). Fig. 5.15 Period of mature permanent dentition.
Fig. 5.15A Complete upper arch with canine and second molar eruption: the green lines indicate the right and left sequential laterotrusive controls, up to the canine dominance.
Fig. 5.15B Complete upper and lower arches (canine and second molar) in lateral view, with class I dental relationships.
Fig. 5.15C Left mediotrusion with canine dominance, disclusion of the posterior sector, sequential effect with disclusion space which increases from the front to the back (disclusion angle).
Fig. 5.15D Skeletal situation: the occlusal structure is fully formed with a final OP inclination and the definitive structuring of the Spee’s curve (blue curve). The TMJ has been structured with a certain inclination and also the proportions between the vertical and horizontal components of the mandible have been re-harmonized. (Edited by: S. Sato, master Course Donau Universität Krems)
The palatal surface of the maxillary canine is usually divided by a ridge, which culminates in the canine cusp with two fossae: a mesial one, on which insists the laterotrusive control with the lower canine, and a distal one, on which focuses instead the protrusive control with the mesial part of the first lower premolar’s buccal cusp. Second molar, upper and lower, erupts upon completion of the upper and lower arches. Usually the upper second molar establishes, at least in the initial phase, a stable contact between its mesiopalatal cusp and the central fossa of its antagonist, without contact between the buccal cusps; so this tooth does not affect the laterotrusive control, which is run by canine dominance. It has been widely discussed about third molars, in relation to the posterior discrepancy concept. Because of this knowledge, it becomes even more determinant a monitoring of patients during their growth phase and an interceptive approach in order to favor the development of a dental normocclusion with a dental relationship of class I. At the end of growth, the system will be developed according to a certain dental relationship, both in the sagittal direction (class I, II, III) and in the transverse one (normal bite, cross bite, scissor bite, edge-to-edge). In turn, the dental relationship will correspond to a mandibular position (skeletal class) and to a subsequent relationship of the articular structures. As previously mentioned, the human body will implement articular, vertical and dental-alveolar compensation’s systems (see Chap. 4) in order to give the eufunction to the system, despite the development of a dysgnathia (not severe).
Fuctional arches and structure of dental arches Slavicek locates in the upper and lower dental arches a series of functional arches that becomes an indispensable tool for the purposes of therapeutic reconstruction of the occlusal surfaces, oriented towards an ideal coordination between the two opposing arches. These concepts are equally important to the orthodontist as in the correction of a malocclusion the
new occlusal arrangement must take them into account. Structurally, in the two arches we can identify continuous functional arches, ranging from the right second molar to the left one, and interrupted arches affecting right and left premolar and molar areas, both on the upper and on the lower arch. On the upper arch we can identify the following functional arches: • Continuous upper passive centric arch This arch is given by the marginal ridges (mesial and distal) and by the fossae of molars and premolars, and by the mesial and distal marginal ridges of the upper incisors and canines. The continuous upper passive centric arch identifies the contact points of the lower active centric arch with the upper arch; then, in a class I dental relationship, the two arches coincide (Fig. 5.16).
Fig. 5.16 Upper passive centric arch: the red line that identifies it, combines the fossae and the marginal ridges of the posterior-superior teeth and the marginal ridges of the upper incisors and canines.
• Continuous functional aesthetic arch It identifies the buccal limit of the upper arch and it is given by the premolars and molars buccal cusps, by the canine cusp and by the incisal edges of the central and lateral incisors; it does not have a corresponding arch in the lower arch. This arch expresses the functional limit within which the mandible moves, and also identifies the boundary between the aesthetic part (vestibular) and the functional part (occlusal) of the upper teeth. On this arch the vestibular surfaces of the upper teeth lie and its amplitude is the support for lips and cheeks (Fig. 5.17).
Fig. 5.17 In green, the functional aesthetic arch, connecting the buccal cusps of molars, premolars, canines and the incisal edges of the upper incisors.
• Interrupted upper active centric arch It is given by the stamp cusps (palatal) of the upper premolars and molars; in the lower arch, it coincides with the interrupted lower passive centric arch (Fig. 5.18). Fig. 5.18 Functional arches of the upper dental arch.
Fig. 5.18A The red dots identify the upper teeth stamp cusps: the blue line that unites them identify the two arches, left and right, of the upper active centric.
Fig. 5.18B Functional arches of the upper dental arch: active centric (blue), passive centric (red) and functional aesthetic arch (green).
On the lower arch, we can identify the following functional arches: • Continuous functional lower active centric arch It is given by the buccal cusps (stamp) of lower molars and premolars, by the canine cusp and by the incisal edges of the lower central and lateral incisors. As described above, in a class I dental relationship it coincides with the upper passive centric arch (Figs. 5.19 to 5.20).
Fig. 5.19 Lower active centric arch: the red dots identify the stamp cusps of the posterior teeth, the cusp of the canine and the incisal edges of the incisors. The line joining them identifies the lower active centric arch.
Fig. 5.20 No coincidence of active and passive centric arches in the tract from first premolar to first premolar, in a case of class II, first division.
• Interrupted lingual arch It is given by the lingual cusps (cutting) of the lower molars and premolars; it has the task of protecting the tongue while chewing and it has no corresponding arches on the upper arch (Fig. 5.21).
Fig. 5.21 Lingual arch identified by the green line joining the lingual cusps of the lower posterior teeth.
• Interrupted lower passive centric arch It is given by the lower molars and premolars fossae and coincides with the interrupted upper active centric arch (Figs. 5.22 to 5.23). Fig. 5.22 Functional arches of the lower dental arch.
Fig. 5.22A Lower passive centric: the red dots indicate the fossae where the upper stamp cusps articulate (in class I relationship), the two blue lines that connect them identify the two arches (right and left) of the lower passive centric.
Fig. 5.22B Functional arches of the lower dental arch: active centric (red), passive centric (blue) and lingual arch (green).
Fig. 5.23 The figure shows the lower active centric arch’s continuity in the upper passive centric arch (red), the correspondence of the upper active centric arches with the lower passive centric (blue). The upper functional aesthetic arch and the lower lingual arch have no analogues in the respective antagonist arches.
Functional areas of dental arches From the functional point of view, the dental arches are divided into three parts: a functional anterior area (incisal-canine), a posterior region destined to the load (molar), and an intermediate zone (premolar). The functional anterior area is extended from canine to canine; in the lower arch, this also includes the first premolar, very similar to the canine tooth, as it has a large buccal cusp while the lingual is smaller and, sometimes, almost absent (Figs. 5.24 to 5.25).
Fig. 5.24 Subdivision of the upper dental arch into functional zones: in green, functional area from canine to canine, in yellow, the intermediate area from the first premolar to the mesio-buccal cusp of the first molar, in red, the load space from the first molar to the second and third molar, if present.
Fig. 5.25 Subdivision of the lower dental arch into functional zones: in green, the functional area which extends from the first premolar to the first premolar, in yellow, the intermediate zone from the second premolar to the mesio-buccal cusp of the first molar, in red, the load space from the first molar to the second and third molar, if present.
The first lower premolar intervenes in protrusive control acting with the mesial slope of the buccal cusp on the distal fossa of the upper canine. In this way the incisor group unloads, especially in the parafunction, transferring the load in a zone and on some teeth more adequate to bear it (Fig. 5.26). Fig. 5.26 Protrusive control in a class III case with a reduced incisors’ control function.
Fig. 5.26A There is a clear relationship between the upper canine distal fossa and the lower first premolar’s mesial slope of the buccal cusp.
Fig. 5.26B The relationship described in Figure 5.26A, during the protrusion, is able to disclose the posterior sector, without the intervention of the incisors’ sector that indeed, in this specific case, is not overloaded.
From the moment they erupt, the first upper and lower premolars are involved in retrusive control, stabilizing the position of the mandible forward. Sometimes it is important to intervene by promoting the establishment of such a relationship with some artificial guides (Fig. 5.14 and Fig. 5.27). Fig. 5.27 Retrusive control of the first premolars and of the first molar.
Fig. 5.27A In red, the cuspal slopes of the upper and lower first molar, involved in retrusive control; in the upper first molar, they are identified in the mesial slope of the transversal ridge while in the lower first molar, they are identified in the distal slope of the distal-buccal cusp (central).
Fig. 5.27B Lateral view of an occlusal relationship of class I in which it is clearly visible the retrusive control of first premolars and first molars.
The protrusive guidance’s function is performed by the distal slope of the buccal cusp of the lower first premolar and by the mesial slope of the palatal cusp of the first upper premolar. The contact between these two surfaces (inclined planes) will facilitate the placement of the palatal cusp of the upper premolar in the distal fossa of the lower premolar, stabilizing the protruded position of the mandible (Fig. 5.27B).
The anterior area of the arches intervenes in protrusive controls with upper and lower incisors (control function), with the upper canine and the first lower premolar, and in laterotrusive controls with the upper and lower canine. The intermediate zone, that is to say the one that affects the upper premolars, the mesial buccal cusp of the upper first molar, the second lower premolar and the mesial buccal cusp of the lower first molar, performs a double function, of load and of laterotrusive guidance, within the concept of sequential occlusion or in possible group functions. The posterior area of the molars, first and second upper and lower molar, mainly performs the function of support to the occlusal load, protecting the TMJ. This division is also found on the sagittal view. The anterior functional area is located in front of the perpendicular to the OP, passing through to the mandible’s genial apophyses (internal part of the mandibular symphysis) (Fig. 5.28). Once again the importance of the OP inclination must be noticed: a wider functional area will correspond to a flatter plane associated to an almost flat SCI. Conversely, a steeper OP will correspond to a steep SCI; tracing the dividing line, the functional area will be smaller and anteriorly shifted (Fig. 5.28A). Fig. 5.28 Functional dividing line.
Fig. 5.28A Perpendicular to the OP passing for the internal part of the mandibular symphysis, the anterior part of it is the functional area. The white lines show a reduction of the anterior functional area if the inclination of the OP increases.
Fig. 5.28B View in the sagittal direction of the dental arches’ functional areas with respect to the perpendicular to the OP. The green anterior area is the functional area; the yellow and red zones (posterior to the perpendicular to the OP) are defined, respectively, intermediate (yellow) and loading (red).
Vertical dimension project according to the Vienna School Introduction This chapter will clarify the concepts they have already been exposed or partially developed in the previous chapters. In particular, here we want to precisely define the management path of the vertical dimension (VD)’s variation, which is a determinant phase of each therapeutic project. The need of varying the VD not only depends on teeth’s reconstructive aspects (lack of space) but, above all, on functional necessities, since the VD is exactly one of the compensatory mechanisms that the human body puts in place to fight the stabilization of the dysfunction that the clinician has to treat or prevent. The vertical compensation is one of the cornerstones of orthodontic treatments with MEAW technique (Sato) and consequently of mandibular repositioning. Below, it will be pointed out that by varying the VD, the characteristics and parameters of other important key elements of function and aesthetics (such as the OP) inevitably change as well, demonstrating that any rehabilitative problematic must always be handled according to the concept of functional and multidisciplinary therapy. The literature argues that vertical dimension variations up to 3-4 mm do not constitute a problem; this reasoning, if generalized and applied without considering the patient’s skeletal type, could lead to outcomes with iatrogenic issues. The change in VD must thus be viewed in the context of a three-dimensional mandibular repositioning, so it is not simplistically manageable only on models mounted on articulator, nor it can be kept within standardized minimum values. In the remaining of the chapter, how to detect and vary the ideal VD will be exposed, in order to achieve positive effects, controlling and managing at the same time the negative ones, in the perspective of an individual functional integration. As already said, the path to follow in order to create the functional project passes through a digital approach, but it still requires analogic models mounted on the articulator and the clinical approach, to be implemented and tested on the patient.
Digital functional smile design (DFSD) The rehabilitation project cannot start from static aesthetic parameters based on dogmatic rules that do not integrate with the individual functional dynamic. Only after having established the vertical dimension (thus its relative skeletal class), the lower incisor edge’s position and having individually set the articulator, it will be the time to build the functional structure, thus having the opportunity to use all the aesthetic canons suitable to handle the vestibular aesthetic part of the teeth, especially in the upper incisor
area. The Vienna School has been using for decades a diagnostic approach (electronic condylography, Figs. 2.78-2.79 Chap. 2) and a digital therapeutic project (see VTO Fig. 3.25); today it is implemented by the IT evolution. Only relying on the aesthetic project, be it digital or analog, the risk of making the mistake of reproducing the pathological malocclusion, which was the cause of the patient’s problems and exposes him/her to big risks and to a iatrogenic dysfunction, is relevant. In fact, those compensations that the system has put in place even at the expense of the tooth structure with severe wear (see Figs. 3.46A-B) will be eliminated. A digital aesthetic project of the upper incisors can be beautiful and comply with all the aesthetic canons, but when it is contextualized on the lower dental arch, it is possible to realize that it is not appropriate. It can highlight a number of issues, including the structural ones, which are difficult to solve without evaluating the functional space (VD) and the dynamics of the system (Fig. 6.1, Case 1). Fig. 6.1 DFSD.
Fig. 6.1A Digital Project of the anterior superior sector.
Fig. 6.1B Contextualizing the aesthetic project with the lower dental arch in ICP, it is possible to understand that to respect the necessary aesthetic parameters, the original deep bite will be re-created.
Fig. 6.1C Only after the VD variation the aesthetic project will contextualize with the function (DFSD).
The same project, with rearrangement of the VD (when necessary), leads to a completely different result, both from the point of view of a contextualized aesthetics and from the point of view of a correct function and of a correct execution of the prosthetic device (Fig. 6.1C). The starting point therefore will be a digital project that starts from the function (Digital Functional Design), but given that the whole process will be aimed at the building of a smile (Smile), it can be defined by the acronym DFSD (Functional Digital Smile Design).
Three-dimensional management of the vertical dimension The evaluation of the vertical dimension on the sagittal profile is the starting point. It is on the LL x-ray tracing that the VD value is measured according to Slavicek (see Fig. 3.23A), but this value is not sufficient in order to have a three-dimensional view of the position of the mandible. An evaluation on the anterior-posterior (very useful in the mandibular lateral deviations, MLD: see Fig. 4.20), and another evaluation on the models mounted on articulator and finally considering the condylographic tracing in dynamics are also necessary moves. The frontal view allows evaluating the right and left VD (basic element in the management of the therapeutic position on the transversal plane) in order to obtain a repositioning of the mandible towards the midline (Fig. 6.2).
Fig. 6.2 VD three-dimensional evaluation. Aligning the two radiographic projections (LL and AP) on the FH plane, the distance between the green line passing through the ANS and the yellow line passing through the PM point,
allows a visual immediate evaluation of the VD entity. On the AP it is also possible to assess the VD difference between left and right in the case of an MLD (red arrows between FH and the line between the left and right antegonial points).
Sometimes it can happen that the VD according to Slavicek is adequate, so that it proves necessary to assess this value according to other reference points, such as the ODI (Sato, Fig. 3.28), that is the angle between FH and mandibular plane, or alternatively the angle between the mandibular and the bispinal plane. It will also be the case to consider whether there are the preconditions for eventual VD’s increases that will always be measured through the conversion table degrees-millimeters on the incisal pin (Figs. 6.3 and 6.4).
Fig. 6.3 Additional reference planes to evaluate the VD. In addition to the classical evaluation according to Slavicek - angle between XI-ANS and XI-PM (blue corner) -, it will be appropriate to assess the DV also among the bispinal plane and the mandibular plane (yellow area), and between the Frankfurt plane and the mandibular plane (green angle).
Fig. 6.4 Conversion table between degrees and millimeters of the incisal pin. In the first row, bordered in blue, the values in millimeter of the incisal pin. In the second line, bordered in red, the values in degrees of the VD from ICP (zero point) and its value when the value of DV varies on the incisal pin. In the third line, bordered in green, the values of the ideal VD to the zero point (ICP)and its variation with the variation of the value of DV on the incisal pin. In the lines below are expressed changes in other parameters as the VD varies, such as the ME, Po and Lower Incisor points’ position.
As pointed out in chapter 2, it is important to determine the starting point, i.e. the “zero point” from which will arise the initial evaluations for the therapeutic program. The zero point will be the ICP, both for the implementation of the radiographies and for the mounting on articulator of the initial models and the implementation of cephalometric and condylographic tracings. All this is essential to be able to objectively quantify the extent of the variations to be made on the three spatial axes, in negative or in positive direction. After having performed the cephalometric tracing according to Slavicek, its digital processing produces a table from which you can determine the starting VD and what should be the ideal one, bearing in mind the individual skeletal characteristics (Chap. 3, Fig. 3.24). At this point, it is possible to convert and then compare the VD value, expressed in degrees by the cephalometric tracing, with the VD value of the articulated models in ICP, expressed in millimeters and measured on the articulator’s incisal pin (Fig. 6.4). Each variation of VD will correspond to a variation of all parameters linked to the mandibular position, that is to say the OP inclination, the lower incisors’ inclination, lips’ profile and mandibular position, dental and skeletal classification (Fig. 6.5).
Fig. 6.5 The table explains how in a patient with VD’s values in ICP of 41.2, to reach the ideal value of 45.1 (violet rectangle) it is necessary to vary the height of the incisal pin as much as 10 millimeters (yellow rectangle).
As already said, the VTO represents the initial step for managing the VD project and the subsequent treatment plan. It is digitally performed, and it proves to be an excellent means of communication within the team in multidisciplinary rehabilitations (including the dental technician). Once the new VD is established, it will be possible to modify on the digital project all the parameters associated with it, adapting them to the new position (Fig. 6.6). In doing so, the new position can be localized on the condylographic tracing, deriving the coordinates from it (Fig. 6.7).
Fig. 6.6 VTO and setting of the VD variation. In the left tracing, it is possible to see the VD’s variation and the opening of a space between the two arches. The right picture shows that, despite the VD’s value in ICP (44.1) being normal, it can be increased for a given skeletal typology always remaining inside the standard values (green area). The value 47.4 will correspond (about +3°) to a variation of about 6 mm on the incisal pin.
Fig. 6.7 TRP position on the condylographic tracing. The blue crosses indicate the TRP position on the tracing, three-dimensionally viewed. In the red boxes on the sides, there are the relative spatial coordinates to transfer the position on the CPV.
The right and left coordinates of the therapeutic position, starting from the ICP, will be set on the variator (CPV) allowing to directly control on the models the new relationships that have been created between the two jaws. It is clear that when the VD is handled three-dimensionally, this will lead to a new mandibular position, that is the therapeutic position TRP. So, when it comes to TRP, we are speaking, inevitably, of mandibular repositioning (Figs. 6.7-6.8).
Fig. 6.8 Left condylar housing of the CPV on which are set the coordinates X -2 and Z +1.7 of TRP, starting from the zero position, i.e. the ICP.
Before going on, there is the need to test inside the mouth, through the TRP test (in the case of splint, splint tests), the new position by means of a key (in wax, thermoplastic material or resin). The key to test the TRP must be executed on the lower dental arch, and through it, it is possible to do a clinical trial and a condylographic one. The clinical test will verify the repeatability of the position and, by palpation, it will re-evaluate the muscular parameters by comparing the registered data to the initial ones (gnathologic chart) (Fig. 6.9).
Fig. 6.9 Splint test executed on the lower arch with Beauty Pink wax; note the indentations on the wax, allowing the position’s control in the mouth.
The condylographic test instead, consists in performing condylographic tracings with the TRP wax test inserted in the mouth (upper dental arch, since the para-occlusal clutch is on the lower arch); removing the wax, standard tracings will be performed and compared among them.
This technique allows, with the patient at the chair, to modify the TRP wax and re-test it with the condylographic tracings. Once the TRP position is set, so as to this procedure can work, whether the models have been mounted in arbitrary hinge axis or in individual hinge axis, the VD’s variation in the articulator has to be performed and tested clinically and possibly also condylographically. Thus, eventually the registration in the mouth of this new RP (TRP) in the new vertical dimension has to be done and the lower model has to be remounted with incisal pin set to zero (case number 1, Fig. 6). In this way it is defined the therapeutic position to work on, i.e. the therapeutic functional prosthetic space. The ideal values of VD are expressed by a Gaussian, bell-shaped curve, therefore a quite large range of variations is obtained, remaining within the scope of normality for each specific skeletal type. In this way, the VD can be increased, by contradiction, also in a high angle if the treatment plan requires it (Fig. 6.10).
Fig. 6.10 The figure shows the possibility of VD’s variation increasing or decreasing it, compared to the ideal value, remaining in the green zone. For the present case, from the minimum to the maximum value there are 11° of difference, which correspond to approximately 22 mm on the incisal pin.
A few millimeters of variation on the incisal pin open a completely different scenario at the functional prosthetic space level applying the OMRT technique that allows the rototranslation of the mandible, eliminating the effect of scissor opening which is obtained with the sole opening in rotation. The interarch space that is obtained by increasing the VD, allows managing the congruity of functional arches (Fig. 5.23) and allows as well determining the correct position and inclination of the OP. This results in a huge benefit for the prosthetic device for what concerns aesthetics, intercuspation, materials’ thickness and the underlying structure. The tooth preparation should take into account the future spatial position of the prosthetic crown, in order to manage it through gnathologically-guided preparations. This concept has to be applied even when the VD is not changed but the characteristics of a functional occlusion (Fig. 6.11) have to be reset anyway. The preparation management in
vestibular-oral direction allows creating the right relationship between the functional arches avoiding situations of almost edge-to-edge between the buccal and the lingual cusps.
Fig. 6.11 Gnathologically guided preparation without VD’s variation (vestibular-palatal view). The left figure shows the initial situation. The figure in the middle shows the asymmetric removal of dental tissue taking into account the occlusal surfaces (larger in the upper palatal area and in the lower vestibular area). In the right figure, the green image with red outline shows the new crowns and the functional arches’ congruency rehabilitation (green circle functional aesthetic arch, red circle in the center lower active centric arch, red circle to the right upper active centric arch). The upper crown was vestibularly displaced, the lower crown toward the tongue.
A proper management in mesial-distal direction allows managing the right dental class relationship. On the vertical direction, the OP inclination can be managed as well. Following this approach, the preparation of the tooth will be more targeted and more conservative and, in the light of the new materials and of the adhesive techniques, also minimally invasive, or even not required (no-prep). The same rules equally apply to implant abutments, if, of course, the implant has been correctly positioned (i.e. in a gnathologically-guided way) (Figs. 6.12 to 6.13).
Fig. 6.12 Vestibular-oral view of VD’s increase. The left figure shows the initial situation. The figure in the middle shows the interarch space that is obtained after the VD’s variation. The right picture shows the restoration of functional characteristics with minimally invasive techniques, or even without preparations (gray area of the right figure); the green dot indicates the functional aesthetic arch. Fig. 6.13 Gnathologically guided preparations. It is a prosthetic reconstruction whose previous preparations had caused an enormous loss of dental tissue.
Fig. 6.13A Occlusal view of preparations with the transparent mask of the wax-up overlapped: the shape of the abutments will allow building a prosthetic device with all the necessary requirements.
Fig. 6.13B Left lateral view of the same case: the present space allows managing the OP inclination in the vertical direction and the dental class relationship in the mesio-distal and vestibular-lingual directions.
VD variation in rotation and in rotational translation If the VD variation is managed only in rotation, a scissor opening effect is obtained, with wide spaces in the incisor area (difficult to handle), and minimum posterior spaces (just sufficient for the new materials, but not for the functional correction). For example, to get a posterior space of 3-4 millimeters, an anterior open of 6-7 millimeters would be provoked, which would be aesthetically and functionally unmanageable. The minimum space of 1.5-2 millimeters, sufficient for the new materials (lithium disilicate) should be allocated between the two occlusal surfaces, superior and inferior, in equal parts, with no opportunity to correct the inclination of the occlusal plane (sometimes the cause of the problem).
So, in spite of rehabilitating the full dental arch, even if with minimally invasive techniques, the possibility to manage the functional prosthetic space will be lost (therefore, to correct the inclination of the OP), to the detriment of the functional problem that required the occlusal rehabilitation. Another problem connected to this type of approach is the management of the anterior open bite that should be treated orthodontically, prosthetically or with a mixed approach. If orthodontically managed, non-functional positions and angles will be given to the incisors, so unstable and with high likelihood of creating dysfunction since the mandibular dynamics is prevented, being the mandible already posteriorly rotated by the VD increase in sole rotation. If prosthetically managed, even with minimally invasive additive techniques, it will be needed to act on the lower incisors by lengthening and inclining them on the vestibular side; but it would cause an alteration of aesthetics and a subsequent flattening of the OP. It must be said that the action outlined above may not be enough to obtain the closure of open bite! At this point, it would be necessary to act on the palatal surface of the upper incisors, increasing their volume and, inevitably, also their inclination. This approach would lead to the onset or aggravation of a dysfunctional problem, because it would be a treatment plan implemented without complying with the functional concepts, which it is necessary instead to refer to. The mixed, ortho-prostetic approach produces the same damage: the damage is actually more serious if the skeletal type is a high angle one. In these cases, the obtained posterior space is very small compared to the large anterior open, but even worse is the articular compression due to the posterior rotation of a mandible already posteriorly rotated. The above described approach as well, thought to manage the open bite that has been created, closes the anterior functional space, preventing the mandible, therefore the system, to implement the relapse, which is a defense mechanism against a therapeutic error (Fig. 6.14).
Fig. 6.14 VD variation in rotation. Note the opening with scissors effect, the considerable space at the incisors’ level, the limited posterior space and the lack of inclination’s management of the new OP (green line) according to individual parameters. Note also the negative effects on the TMJ with compression and possible anterior displacement of the meniscus.
If instead the intervention will be oriented on rototranslation’s movements, it will be
possible to get variations of the vertical dimension considerable at the posterior level, useful to the resolution of all the rehabilitation’s issues. The posterior space that is obtained is related to the SCI, without excess of negative OJ and OB (open) as the counterclockwise rotation of the mandible that follows the verticalization, allows a reduction of the anterior space by canceling the scissor effect (see Figs. 1.19-1.20C). The space’s opening at the posterior sector level depends on the eminence’s inclination: it will be greater with steep SCI and, vice versa, smaller with flat or less steep SCI. Knowing the SCI in advance is crucial to examine the effects of the VD variation planned in the rehabilitation treatment. The three-dimensional repositioning of the mandible can be achieved especially in classes II, only if the posterior occlusal plane is flattened, with increased reliance on the upper arch (Figs. 6.15 to 6.16). To stabilize the mandibular position, the posterior support must be recreated with the right OP inclination.
Fig. 6.15 VD variation in rotational translation. Note the opening of an almost identical interarch space in the various sectors. The anterior open is minimal or inexistent. The forward mandibular movement unloads the TMJ. The possibility of managing the new OP inclination (green line) is evident, asymmetrically dividing the space between the two arches. Fig. 6.16 Comparison on the articulator of a VD variation of +4 mm, in rotation and in rotational translation.
Fig. 6.16A Variation in rotation; note the mandibular posterior positioning with worsening of the dental class relationship towards class II and the considerable space in the incisors’ sector.
Fig. 6.16B 4 mm variation, but with an advancement of 1 mm (translation) on the same model: note the uniform opening of the posterior space and the counterclockwise rotatory effect due to the translation, leading to the closure of the anterior open. The contact between the incisors highlights the functional problem, caused by the upper incisors, which are too steep and lingualized.
The other huge advantage deriving from the mandibular shift, especially in skeletal high-angle types, is the temporomandibular joint decompression. In the classes III low angle (or tending to it) instead, the VD’s increase, with greater rotatory component, is preferable as it decreases the anterior deep bite and increases the OP inclination, which is an indispensable characteristic to obtain a mandibular repositioning towards a skeletal type of class I (or tending to it).
Dental and skeletal class variation and variation of incisors and OP inclination As said, the variation of the vertical dimension is a very important compensatory mechanism in the correction of malocclusions. Its variation must not be taken into consideration only when space for the materials is needed but, above all, for therapeutic purposes. This variation must be established before the prosthetic project because, depending on the extent of the variation, the entity of variation will provide considerable differences of the skeletal class and, therefore, of the dental class as well (Fig. 6.17).
Fig. 6.17 Variation of the dental and skeletal class and new OP inclination after the verticalization. To the left, the initial situation, in the center, the dental and mandibular relationship’s variation, to the right, the OP inclination’s variation and the new created space. Being the opening in rotation, here all the negative elements related to the
method of VD’s variation only in rotation are highlighted.
How it will be noted in the description of the clinical case 1, a variation in the DV is able to transform a class III in a class I and its three-dimensional management allows recentering the mandible on the midline. These aspects need to be quantified before preparing the teeth or inserting implants, otherwise the risk of filing the teeth where it should not be done is taken and also the risk of inserting implants in wrong positions, with negative consequences on the prosthetic structures. The change of the mandibular position, induced by the VD variation, will also produce the change of the gnathologic OP (lower incisor-lower first molar’s distal cusp) position and inclination. Consequently, the need for the gnathologic OP’s correction and relocation in the interocclusal space between the two dental arches will be generated, always starting from the redefinition of the lower incisor edge’s position. In the incisal area, following the VD variation, the overjet and over-bite relations change: the effect is due to the lower incisor that moves together with the mandible. The VD variation in rotation causes the steepening of the gnathologic OP, which has a strong negative effect in classes II, especially those high-angle (or tending to it), as the anterior repositioning of the mandible is hindered. The anterior open bite determined by an increase of the VD only concerning the rotation is difficult to manage both prosthetically and orthodontically speaking, because it interferes with the aesthetics (teeth too long) and with the function (absence of functional space with blocked arches and excessive mandibular posterior positioning) (Fig. 6.18).
Fig. 6.18 Closing scheme of the anterior open after opening in rotation. Occlusal plane too steep (green line), excessive closure of the functional space, which significantly affects the mini aesthetics (lips-teeth), especially when the incisors’ sector has little or no wear.
The change of position and inclination of the lower incisor that follows the verticalization, affects the OP characteristics. Note that OP inclination can be changed while keeping the posterior point (first molar) fixed
and changing the anterior point (incisor) or doing the reverse path, or by acting on both points. So, the lower incisor lengthening aimed at closing the open bite that follows to the verticalization should be carefully evaluated for its negative effects on OP’s inclination and position.
Gnathologically-guide dimplantology concepts Starting from the concept that the implants must replace the missing tooth, in complex cases, like in all other prosthetic rehabilitations, it should be taken into account the need to establish the therapeutic position, thus the entity of the mandibular repositioning to be carried out. In view of the mandibular repositioning the evaluation of the implant position should not be made in the initial pathological mandibular position (ICP), but in the ideal therapeutic position (TRP). Given the transversality of gnathologic concepts to all the branches of dentistry, it must be said that even implantology uses them. Thus, the switching from a prosthetic-driven to a gnathologically-guided implantology, closely linked to the concepts of mandibular repositioning, skeletal class and vertical dimension, will occur automatically. It is important that every implant is three-dimensionally positioned in an ideal position so that the occlusal surface of the prosthetic crown that it will have to support can intercusp with its opponent according to an appropriate occlusal relationship, both in sagittal and transversal direction, as it was a natural pillar. The ideal therapeutic position will be found on articulator before that the implants are placed inside the mouth. To this aim, it will be crucial to pre-treat the patient with splints or provisionals, for deconditioning the system and making the TRP transferred into the oral cavity an objective reality, not just a digital project. The ideal gnathologically-guided implant placement still leaves an eventual minimum correction possibility open to the technician, who will act in bucco-lingual and mesial-distal direction on the implant’s abutment, which is always gnathologically-guided as well (Fig. 6.19).
Fig. 6.19 Gnathologically guided abutment. Abutment’s construction on the basis of the gnathologic wax-up: in this way the prosthetic crown, integral and/or with substructure, will have all the requirements to fulfill its role.
To confirm the fact that implantology must be gnathologically guided, Slavicek’s studies
exist, conducted by means of the results of CT examinations, in transversal section in the first molar area; these studies confirm that the physiological distribution of the first upper and lower molars’ roots follows strict rules. In particular, the vertical loads transmitted while closing from the lower to the upper molar, unload themselves from the mesio-palatal cusp, through the palatal root, on the palatal vault. The buccal roots of the upper molar absorb instead transverse loads unloading them on the zygomatic process (Fig. 6.20). Considering the orientation of the lower teeth in sagittal direction their mesial angle will be noticed, within the law of Page, because their dental axis is perpendicular to the closing axis. If this principle is valid for the lower incisor, studies conducted by Orthielib state that molars and premolars have, between their dental and their closing axes, an angle greater than 90°. Fig. 6.20 Diagram of a cross section CT scan at the level of the first molars.
Fig. 6.20A In red the palatal root of the first upper molar that with its mesiopalatal cusp goes in the central fossa of the lower first molar. The blue arrow indicates the unloading direction of the masticatory loads on the palatal vault through the palatal root. The red dots indicate the inferior alveolar nerve’s path while the small blue arrows indicate the submylohyoid recess.
Fig. 6.20B Implants’ insertion in upper-lower first molar position according to functional gnathologic canons similar to those of the natural tooth.
Fig. 6.20C Correction with abutments of implants’ inclination according to the gnathologic principle.
Fig. 6.20D Definitive crowns with perfect mating of the stamp cusp in the antagonist’s fossa, according to gnathologic canons.
Even the sagittal view confirms that chewing loads unload from mesio-palatal cusp through the palatal root, on the palatal vault (Figs. 6.21 to 6.22). Taking into account the physiological angles that teeth have on the transverse and sagittal planes, the surgical procedure of implant placement in these locations will be greatly facilitated. Therefore, following the gnathologically-guided placement’s process, the surgeon could get the indication to insert the implant where the conditions of the residual bone ridge would not allow it.
Fig. 6.21 Teeth position with their axes perpendicular to their respective closing axes (red lines). Variation according to Orthielib (green lines) given by the blue angles (differential angles). The differential angle for the lower incisor varies depending on the skeletal classes (Fig. 3.42).
Fig. 6.22 Diagram of forces’ unloading at the level of the first molars and correlation with the incisors’ sector.
In these cases, techniques of increase in bone volume with regenerative techniques must be used, or also bone tissue’s grafts techniques: about these subjects, the clinical experience of the writer is inclined towards split-crest techniques combined to the use of implants of reduced diameter, in extreme cases. The volume increase of the residual ridge, acting on hard and soft tissues, is an indispensable prerequisite for a proper implant placement (Fig. 5.C Case 3). Proper dental arch’s width allows for a better unload of the forces, a better aesthetics at the intraoral soft tissues (gingival architecture) and perioral (lips) tissues’ level, produces an improvement in facial macro aesthetics and creates the optimal conditions for the hygienic maintenance of the prosthetic device. All these factors create the conditions for the long-term success of implant therapy. Of course, a wide upper arch allows having a suitable aesthetic functional upper arch, which goes to the benefit of aesthetics, ensuring a mandibular physiologically more advanced position, to the full benefit of the lingual posture. According to this approach, it is easier to adapt to the remaining anatomy, limiting the surgical invasiveness and decreasing the risks, with the huge benefits listed below: • Implant positioning according to the physiological position of the dental roots; • compliance with functional load axes; • surgical advantage as inclining the implants in the first-second molar area in lingualvestibular direction the need to regenerate the bone vestibularly is lost (it may be sufficient split-crest, or smaller implant diameters); • in the case of the upper molar, maintaining the implant inclination towards the palatal vault, the palatal wall of the maxillary sinus can be exploited to increase the bone volume; • the submylohyoid recess and the mandibular canal in the lower molar area are avoided; • the surgical action is eventually facilitated with respect to the straight insertion as the inclination of the mesial and lingual micromotor requires less space, so less mouth’s opening. The gnathologically guided implant placement is even more important in the aesthetic sector
(incisor-canine): in addition to the listed benefits, it allows to obtain a better aesthetic result, of course with a cemented and not screwed crown. Even in the anterior area, the implant insertion implemented in respect of the natural angles of the teeth, allows the better exploitation of the residual bone, making use, to the maximum, to split-crest techniques, and avoiding the use of much more invasive regenerative therapies (Fig. 6.23). The implant insertion that respects the normal inclination of the upper incisor root allows placing the crown in a more vestibular area by restoring the proper support for the lips to the advantage of the macro-mini facial aesthetics and of the function (Fig. 6.24). From the foregoing reasoning emerges the fundamental importance of the first molar in the management of the chewing loads on natural teeth but, even more, on implants. It is crucial that in complete rehabilitations, the occlusal surfaces must provide the recovery at least until the first molar. By following these principles, the design choice will inevitably fall into cemented and not screwed solutions, especially in the upper incisor area; therefore it will be again the function to dictate the clinician’s orientation.
Fig. 6.23 Implantation in the upper incisors’ area. The left figure shows how an implant insertion, respecting the natural incisor’s physiological direction, inevitably leads to a cemented prosthesis, using the crest’s expansion technique (gray vestibular part). The right figure illustrates the straight type of insertion, which leads to a screwed prosthetic choice and highlights the need for regenerative surgical techniques (GBR). Fig. 6.24 Gnathologically guided implantology.
Fig. 6.24A Implantation in the incisors and first molars’ area following functional axes, compatible with the chewing forces’ axes of natural teeth (yellow and purple lines).
Fig. 6.24B Implantation according to a straight axis, identifiable by the red line, which has angles completely different from the natural ones, compared to the closing axis.
Occlusal Mandibular Repositioning Technique OMRT (Bassetti) Introduction Let us focus our attention now on the concept of Reference Position (RP) providing the opportunity to look at a new position, for therapeutic purposes, passing from the RP to a new location, called Therapeutic Reference Position (TRP). In practice, the aim is to design the TRP through the mandibular position’s variation in the three spatial axes. Reiterating that all the presented concepts are transversal to all the rehabilitative branches, including orthodontics, in this new position there will be a space to manage between the upper and the lower dental arch, called Functional Prosthetic Space (FPS). We would point out once again the OP management concept, which favors the mandibular repositioning. Therapeutic aids that the clinician may use in order to reach his/her targets will be: Splint for Mandibular Repositioning, Therapeutic Provisional and Rehabilitative Orthodontics with MEAW technique, as well as the reassembling technique on the CPV of the therapeutic position until its stabilization, before proceeding with the final rehabilitation. Furthermore, the crucial moment of prosthetic rehabilitation, that is to say the TRP transfer from the mouth to the models mounted on articulator, will be dealt with. Finally, as a demonstration of what has been said, the Early Mandibular Repositioning Technique (EMRT) will be introduced; this technique allows, through the early management of functional space, guiding the movement of the mandible to an ideal TRP and the promotion of a functional growth tending towards a skeletal class I.
Reference Position (RP) and Therapeutic Reference Position (TRP) concepts The starting point for mounting the models on the articulator is the position of maximum intercuspation ICP or habitual occlusion: the maximum intercuspation position is compared to the position of the models mounted in Reference Position. The Reference Position is defined as the unforced position in which the condyle is on the disc and both, disc and condyle, are against the eminence without load (Slavicek). It is a position completely independent from influences dictated by the occlusal relationship, solely dependent on the ligaments and muscles of the cranial-mandibular system (CMS), i.e. the anterior temporal muscle, the deep masseter (zygomatic mandibular muscle) and the upper head of the lateral pterygoid. These muscles act on the mandibular posture, but not in eccentric movements; they are active in the closing phase, centering the condyle on the disc and stabilizing condyle and disc against the articular eminence. The RP must be a repeatable and physiological position, therefore it will have to indicate the starting point for establishing
the final therapeutic position. For a proper registration, the patient is positioned on the dental chair with back and head well flat and with a backrest angle of about 45°. The next step is the deconditioning of the system which is obtained by asking to the patient to make opening and closing, protrusive and retrusive movements, to re-lubricate the articular compartments. Finally, two cotton rolls are fitted between the dental arches (right and left) and the patient is invited to close loosely the mouth for about 4-6 minutes in order to eliminate the proprioceptive influences of the occlusion (Fig. 7.1). Sometimes the starting point is a position in which the RP position cannot be reached, so that it is called Deranged Reference Position (DRP). Inchapter 2 it was explained how to proceed to register a RP and how to transfer this relation on the models mounted on articulator. The difference between the two positions, RP and ICP, can be evaluated with the CPM, with the condylar position variator CPV, or electronically with the condylograph. Having mounted the models in ICP, this will be considered as the “zero point”. The articular condylar housings of the variator (CPV) must then be unlocked and the upper model interfaced, through the RP wax, with the lower model. The condyles of the variator will finally be reintegrated to the relative condylar housings, which will then be locked again. Fig. 7.1 RP’s registration.
Fig. 7.1A Patient and clinician hand’s position for recording the RP without forcing the system.
Fig. 7.1B RP registration scheme; note that the movement between points A and B is just rotational (red path); to remain in this range it is crucial to use thin layers of recording wax.
At this point, it will be possible to read the obtained values in the three spatial dimensions, X-Y-Z, and the VD value on the incisal pin. The measured numeric data allow the quantification of the three-dimensional difference between ICP (zero) and RP and it will also be possible, moving on the three dimensions of space, to evaluate the future therapeutic position and the VD variation, measured on the incisal pin. In the past the difference between ICP and RP was quantified at around 1.3 mm; therefore, while varying the vertical dimension, the mandibular position in the three spatial dimensions was limited, remaining close to the rule ICP = RP (Fig. 7.2).
Fig. 7.2 Diagram showing the minimal difference between RP and ICP; note that the minimum displacement of the arches does not produce effects at the TMJ level.
This rule was especially observed in prosthetic rehabilitation; regarding this subject, the Vienna School has prepared occlusal reconstructing techniques in I-II-III class in normal bite, or possibly in cross bite. In the orthodontic approach according to Sato’s philosophy, with the aid of the MEAW technique, this rule is subverted as from the ICP and the initial RP it is possible to move towards a new therapeutic position (TRP), allowing the correction of a full class II in a class I through mandibular repositioning. All this is possible by giving to the system the possibility of implementing the articular compensation mechanism (Chap. 4). In order to realize this compensation, it is important that the anatomy of the occlusal surface is well defined so that the occlusion can stabilize the obtained TRP position.
Functional space and vertical dimension The functional space is the ideal space, located between the upper and lower jaws, dictated by an individual value of the VD. The mating between the upper and lower arch divides the space into an inner part, occupied by the tongue, and an outer or buccal part, bounded posterior-laterally by the cheeks and anteriorly by the lips. The inner part, which determines the functional space for the tongue, depends on the VD and on the amplitude and position of two functional arches, the lower active centric and upper functional aesthetic ones (Chap. 5). The functional prosthetic space is thus correlated to the intermaxillary relationship in the final therapeutic position (Fig. 7.3). Fig. 7.3 Functional prosthetic space.
Fig. 7.3A Functional prosthetic space view on the lateral of the skull in a case of full denture. Notice its dependence on the VD and on the related skeletal class.
Fig. 7.3B Schematic view of the functional prosthetic space; the yellow lines identify the two jaws, the red dot identifies the TMJ.
This relationship, as seen in previous chapters through the assembly of the models on articulator, can be transferred from the mouth to master models, mounted on articulator in TRP. Once assembled the models on articulator, there will be a space to manage, completely empty in the case of full dentures and complete rehabilitations on implants, or with the presence of compromised natural teeth to be rehabilitated. The functional prosthetic space can also become functional orthodontic-prosthetic space when, following a multidisciplinary approach, the orthodontist’s intervention is required (Fig. 7.4). Fig. 7.4 Functional prosthetic space on models mounted on articulator.
Fig. 7.4A Lateral view of the space to manage.
Fig. 7.4B Space completion according to gnathologic canons.
The space management goes through two phases: • Step 1: evaluation and measurement of its amplitude (VD); • Step 2: preparation of a new space to be managed according to functional parameters. The first step, in turn, can be divided in two moments: 1. identification and possible variation of the Vertical Dimension (VD); 2. assessment of the skeletal class in initial and therapeutic VD, so as to get the right threedimensional relationship between the two dental arches and to establish the consequent dental class relationship. The second phase, namely the prosthetic space’s construction according to the functional parameters, includes instead the following moments: 1. lower incisor’s positioning with incisal edge of 1-1.5 mm beyond the lower lip, testing it in the mouth (its inclination must respect the closing axis’ rule);
2. OP inclination’s management correlated to the SCI, and positioning of the lower first molar; at this point the distribution of space between the upper and lower arch has been automatically carried out. In this way, the lower dental arch, defined by the lower active centric arch, can be completed; 3. upper incisor’s positioning according to functional (S1-S2 correlated to the SCI) and aesthetic parameters; 4. completion of the two arches’ occlusion according to the established functional design (sequential occlusion with canine dominance). All the process described above is carried out on the patient’s natural teeth, on implants or even on edentulous arches; it can be also applied in orthodontics (Fig. 7.5). Fig. 7.5 Construction highlights of the functional prosthetic space.
Fig. 7.5A Lower incisors and lower first molar positioning (blue) with the OP definition and the lower arch’s completion.
Fig. 7.5B Upper incisor positioning (blue) with the inclination of the palatal surface (green line) which respects the gnathologic principles.
Fig. 7.5C Upper arch completion according to the designed dental class relationships.
If each operating step is performed within the functional parameters, the mandible will find the right spatial collocation for the benefit of a proper lingual posture, an adequate space for the airways, and supra- and subhyoid muscles’ relaxation (the hyoid bone’s repositioning demonstrates this last point). The benefit will also be assured for the mimic muscles and for the facial macro-aesthetics, also allowing the three-dimensional reorganization of the cervical spine.
Occlusal plane and vertical mandibular repositioning
To implement the mandible repositioning and contribute to its stabilization in therapeutic position (TRP), the management of the following aspects must be taken into account: • OP inclination; • posterior support (VD); • retrusive control at the level of the upper and lower first molars; • protrusive guidance and retrusive control between the lower and upper first premolars. As mentioned in chapter 3, the inclination of the occlusal plane must be related to the SCI, according to the relative skeletal type. Assuming that a steep posterior occlusal plane generates a class II, the decrease in its inclination eliminates the posterior interference, allowing an anterior repositioning of the mandible. Considering instead that a flat posterior occlusal plane generates a class III, the increase in its inclination allows a posterior repositioning of the mandible. In both cases, the articular compensation is involved, compensation that can be effective only if any possible variation in the vertical dimension (vertical compensation), in the OP inclination and in the posterior support’s recovery is accounted for. Obviously, this can be obtained in the presence of natural or artificial cuspidate, not flat teeth. After having detected the OP inclination, and since it is placed on the mandible, it will be necessary to take into account the fact that any VD variation will cause an OP inclination’s variation (Fig. 7.6). Fig. 7.6 Mandibular repositioning in an orthodontic-prosthetic case.
Fig. 7.6A Initial situation with accentuated inclination of the posterior OP and mandibular backward positioning (class II).
Fig. 7.6B Intraoral situation that highlights the new occlusal relationship of class I after the OP inclination’s correction and the restore of posterior support with an implant on the lower first molar.
Upper and lower first premolar’s role in mandibular repositioning The key to stabilize the mandible in TRP is represented by the occlusion; more precisely, the occlusion crucial point is located between the upper first premolar’s mesial slope of the palatal cusp and the lower first premolar’s distal slope of the buccal cusp. From a Professor Sato’s original drawing presented to the IAAID ASIA 2009 Congress, it is possible to derive the importance of the anatomical shape of the upper and lower first premolar to obtain a stable mandibular repositioning, both in prosthesis and in orthodontics (Fig. 7.7). In prosthetic rehabilitations, the teeth cannot be flat, they must present instead cusps with angles of about 30°-25° so that they can perform their specific role. In adult orthodontics, this prerequisite may not be present due to natural teeth’s abrasion; then it will be appropriate to restore it by reconstructing the cuspal slopes and the cusps with direct composite, respecting the adhesive procedures and using silicone masks, made from wax-ups performed on the
articulator. This procedure allows, during treatment, to implement addition and subtraction’s changes in an easy and economic way, maintaining the option to possibly replace, at the end of the therapy and with stable therapeutic position, the direct composite with ceramic materials or with composites obtained with indirect techniques. If the key is in the first premolars, it is good to extend the concept of protrusive guidance also to the second premolar and to the first molar. These guidance’s areas are located in an occlusal class I relationship on the distal slopes of the lower buccal cusps and on the mesial slopes of the upper palatal cusps (Fig. 7.8). The use of direct composite to restore the residual teeth’s occlusal anatomy in adult patients, both in prosthetic and in orthodontic therapy, is a pivotal step to support and stabilize the mandibular repositioning.
Fig. 7.7 IAAID Asia Congress (Tokyo 2009). Professor Sato’s drawing that highlights the importance of the occlusal relationship between the first upper and lower premolars in order to favor and stabilize the mandibular repositioning, avoiding Wilson curves with negative values. Fig. 7.8 Protrusive guides of the first premolars.
Fig. 7.8A Premolar control’s stabilization (class I) in children (i.e. developmental stage, internal vision).
Fig. 7.8B View on the models of the first lower premolar relationship with its antagonist for retrusive control and for protrusive guidance; lower first premolar relationship with the upper canine for protrusive control. It is also well visible the first molars, upper and lower, retrusive control.
Fig. 7.8C The diagram illustrates the protrusive guidance of the first premolars. The green dot indicates the first contact in the retral first contact position (RCP), the red arrow indicates the sliding in ICP (red dot) of the lower first premolar through the distal slope of its vestibular cusp on the mesial slope of the upper first premolar’s palatal cusp. This leads to a mandibular advancement resulting in a joint compensation evidenced by the shift from the green to the red dot along the protrusive tracing (light blue).
These materials, when the adhesive techniques made under dental dam are properly performed, can remain in the mouth for many years because, unlike ceramic materials, they ensure an excellent adaptation besides the possibility of their modification. The clinical long term verification of the direct composites shows that it is important, in addition to the physical characteristics of the used materials, the functional context on which these composites operate (Fig 7.9).
Fig. 7.9 Direct composite reconstruction of the 43-33 sector after multidisciplinary treatment with mandibular repositioning.
Fig. 7.9A Initial situation.
Fig. 7.9B Reconstruction with the aid of a transparent silicone mask, derived from the wax-up.
Fig. 7.9C Direct composite restorations’ control of the 43-33 group after five years: the situation is stable despite the bruxism. Note the improvement of the gingival recession on the 31 following the proper function’s recovery.
Thanks to the protrusive control and to the concept of incisors’ control (and not that of incisors’ guidance), the incisal sector is not subjected to abnormal forces, which it is not intended for, resulting in a preservation of the restorative materials and of the natural teeth. The recovery of a correct function, together with an occlusion capable of controlling the parafunction, ensures the long-term success. If necessary, the possible wear can still be compensated for with a new material intake, re-using as a guide the silicone mask used for the reconstructions’ realization.
Splint for occlusal mandibular repositioning
In complex cases, like those with strong symptoms of pain and those with articular locking, the pre-treatment with splint remains the best choice to test the therapeutic position and to decondition the system, without resorting to irreversible changes. The pre-treatment is also crucial in patients with a strong psychological component as it allows testing the therapeutic project and, if necessary, cancelling the treatment without having caused irreversible changes of the initial state. Unfortunately, when there is not the possibility of recreating support with the splint because of missing teeth, removable or fixed prosthetic solutions have to be founded and the pretreatment has to be implemented with temporary prostheses, whether they be fixed or removable. The splint will be placed on the lower dental arch because, in doing so, the functional schemes do not change and there is very little interference with phonation and aesthetics. All this causes the splint to be worn during the relational life, increasing the success of this type of therapy (Fig. 7.10). The verticalization with the splint must be done on the basis of the cephalometric tracing, precisely considering the initial vertical dimension.
Fig. 7.10 Lower splint inserted into the mouth in a case with severe deep bite (Fig. 1.5A Chap. 1); there are no hooks, retention is achieved by exploiting the undercuts in the premolar-molar area.
Sometimes the splint cannot completely resolve the symptoms because in very deep bites, in addition to the verticalization, a mandibular advancement beyond the incisors’ edge-to-edge is required. In these cases, the patient must be made aware of the need for an orthodontic treatment as definitive therapy. Another limitation of the splint is that it cannot correct the OP inclination, which represents an indispensable condition to favor a mandibular repositioning. In classes II high-angle, the splint increases the posterior mandible rotation (clockwise) creating an additional impact of the condyle against the articular eminence and an increase of the anterior open bite; this could also produce an accentuation of symptoms (Fig. 7.11).
Fig. 7.11 High-angle case where a splint built opening just in rotation has been applied; notice the mandibular backward positioning and the excessive intercuspation that prevents a mandibular repositioning in protrusion.
Conversely, applying also in the therapy with splint the same Sato’s orthodontic concepts for the OP and for the VD control (creating a posterior support and avoiding to steepen the occlusal plane of the splint in the molar area), an anterior mandibular rotation will be obtained, unloading in this way the TMJ. In these cases, to push the mandible in the therapeutic position favoring the re-education of the system, it will be necessary to build on the splint some protrusion guides in the premolar area (Fig. 7.12). Fig. 7.12 Protrusive guides and retrusive controls.
Fig. 7.12A Notice the inclined plane on which acts the mesial slope of the first upper premolar’s palatal cusp, explicating the retrusive control and the protrusive guidance. In addition, the inclination of the splint in the anterior region correcting the excessive steepness of the upper incisors and canines’ palatal surface is visible.
Fig. 7.12B The arrows indicate the left and right inclined planes on which act the premolar control: also notice the slight intercuspations with the stamp cusps of the antagonist teeth.
Even in therapies with splint it should be noted that when increasing the vertical dimension there is not only a clockwise rotation with posterior displacement of the mandible. To the rotation in fact must inevitably follow a mandible’s displacement forward, with counterclockwise rotation, capable of unloading the TMJ (with essential increase of posterior support). The therapeutic position’s stabilization with the splint has to go through splint reassembling steps on the variator (CPV), making any necessary addition or subtraction of resin (Fig. 7.13).
Fig. 7.13 Registration on the splint of the therapeutic position with Aluwax® wax, in order to perform the reassembling on the CPV, on which the contacts’ adjustments will be performed.
When the symptoms will moderate themselves or even disappear, the patient will be able to: a) choose to postpone the definitive therapy continuing to wear the splint, which will be periodically checked (about every 3-4 months); b) decide to move to the definitive therapy and in this case the clinician will follow a
specific multidisciplinary approach.
Therapeutic provisional When it comes to mandibular repositioning, the provisional plays a pivotal role, both in fixed and in removable prosthesis. The provisional is responsible for the management of the functional prosthetic space and guarantees the three-dimensional repositioning of the mandible through the technique of its re-mounting on the articulator or, even better, on the CPV (Fig. 7.14). Fig. 7.14 Biological function of the provisional in case of implants.
Fig. 7.14A Provisional screwed on implants with an appropriate form of its cervical part apt to the peri-implant tissues’ conditioning.
Fig. 7.14B Effect on peri-implant tissues obtained managing the cervical part of the provisional.
The therapeutic provisional underlies the following main functions: • biological, given its cervical part; through this function, also the tissue conditioning
functions, both on implants and on natural teeth, are exerted; • aesthetic, especially regarding teeth’s volumes and position; • functional, performed in particular by the functional information entered on teeth’s occlusal surfaces; • definition of the TRP by means of the reassembling on articulator technique. After having made a diagnosis and set a treatment plan, the therapeutic provisional will be built. The information from the project will be included on the provisional device (OP inclination, upper incisors’ S1-S2 tract inclination, protrusive, laterotrusive and retrusive controls) and used to recondition and bring the stomatognathic system to the healing. All the process will pass through the test inside the mouth and then, as the system will proceed to its deconditioning, the new position will be tested with the reassembling technique and stabilized again with additive or subtractive adjustments. All the necessary adjustments will be made on articulator, not in the mouth, demonstrating that the pathological system is oriented toward healing by the clinician (Fig. 7.15). For example, in a lateral deviated system, if the conditions for the mandibular recentering are not fitted on the provisional, the recentering will not happen: the pathological position will be maintained, believing that it is the ideal one for the system, because of the lack of additional information and deconditioning.
Fig. 7.15 Management of the functional prosthetic space with the therapeutic provisional (left side) in order to allow the realization of the final device in the same TRP (right side).
Therefore, it is not recommended to make adjustments inside the mouth with articulating papers because the system does not decondition itself and any retouching made could maintain the same pathological situation, without variations. The adjustments must be performed instead through the provisional mounted on the articulator, which has to be set individually, after having performed an intraoral registration of the therapeutic position. Even full dentures must necessarily pass through the therapeutic provisional, which will be built ex-novo, or using the old denture with the sandwich technique (Fig. 7.16).
Fig. 7.16 Therapeutic provisional in full dentures made with sandwich technique that allowed an increase of the VD up to 15 mm.
CPV use in reassembling technique The occlusal mandibular repositioning technique (OMRT) implies the CPV’s use because this tool allows the assessment of the mandibular position recorded with the “patient to the dental chair”, consenting any eventual change to the splint or to the provisional. This phase does not require a new models’ mounting on articulator, as the basis on which the provisional or the splint were built will be re-used. On the CPV, however, only centric relations, not the dynamic movements, can be managed. In case it was necessary to manage the dynamic occlusal relationship through the inclination’s control of the mediotrusive and protrusive guides, it would be mandatory to switch from the CPV to the articulator, which can be individually set. It is convenient to always make a first assessment of the TRP of the provisional on plaster models mounted on the articulator; only after this check, the impressions that will allow obtaining models with the provisional inserted on them will be taken (Fig. 7.17). The plaster models with the therapeutic provisional at this point will be mounted on articulator, in ICP position. Fig. 7.17 Evaluation of the difference between ICP and TRP on plaster models.
Fig. 7.17A Intraoral situation in ICP; if any control was effectuated in the mouth with articulation paper, it would detect the presence of contacts.
Fig. 7.17B On the contrary, the mounting of the lower model with RP wax shows a space, i.e. a lack of support.
Fig. 7.17C Test inside the mouth of material’s replacement to be carried out on the right lower provisional; this will allow a repositioning of the mandible forward and to the left, recentering the midline.
The next steps to perform will be: • detecting the TRP position into the mouth; • unlocking the CPV’s articular condylar housings on the three axes X-Y-Z; • assembly of the models (upper and lower) with the TRP registration wax; • repositioning of the condylar housings, screws’ locking; • assessment of the relationship between the dental arches at first contact. At this point, on the condylar housings it will be possible to read (on the three spatial axes) the value of the differences between the condylar position in ICP and the condylar position in TRP. It will be necessary to remove any interference until reaching the desired position; where there was no contact, it should be re-stored (Fig. 7.18). Fig. 7.18 Phases of the reassembling technique of the therapeutic provisional (therapeutic prosecution of the case shown in Fig. 7.17).
Fig. 7.18A Impression with the provisionals and elimination of the undercuts with wax before pouring the plaster.
Fig. 7.18B Model on which are inserted the provisionals; the occlusal surface is covered with Aluwax® wax used to register the TRP.
Fig. 7.18C Models with provisionals on CPV, ready for the necessary corrections.
Fig. 7.18D Variation of the condylar position from the ICP to the TRP; the left condyle does not undergo displacements on the X and Z axes, the right condyle moves 2 mm along the Z axis and 1 mm along the X axis, so the mandible tends to recenter on the left side.
The CPV lets the clinician to change the condylar position toward a new TRP and to adjust the provisional, by addition or subtraction of material, in the new occlusal relationship. In this phase, as mentioned earlier, it is essential to have the lower model with the three pins (Chap. 2) so as to be always able to work on the same model and to preserve all the mounting plates to check again all the modifications made. Therefore, once the relationship between the two arches on the CPV in the new TRP is stabilized, the position key is detected (for example with Temp-Bond®, or with Aluwax® wax) and is used to reassemble the lower model on the articulator with incisal pin set to zero. At this point, always by material’s subtraction or addition, the protrusive (upper incisors) and the laterotrusive (upper canines) controls will be individualized. In this way we also enter in the context of the mandibular dynamics parameters.
From the therapeutic provisional to cases’ finalization Once an asymptomatic and repeatable therapeutic condition, confirmed by clinical and instrumental parameters, is reached, this will be the “ideal” position for the case’s finalization. Both the master and the provisional models will have to be built with individually separated teeth, according to the antagonist pin model’s technique. The next step of this process will be the transfer of the TRP from the mouth on the master models mounted on articulator. A precise transfer of the TRP from the mouth to the articulator is crucial both for the assembly of master models and for the assembly of master models with provisional ones (cross-mounting technique with the provisional models).
Therefore it is crucial that the position to be transferred on the articulator should be strictly that of the therapeutic provisional: for this purpose, the TRP registration technique by sectors through the provisional is used, in order to keep the ideal position reached. This technique allows reproducing in a very accurate way the mandibular position in the vertical (VD), transversal (left-right), and sagittal (forward-backward) directions, and also avoids the possible mandible’s tilting, to the right and to the left. Following this operational path, the patient’s interference, that could lead to an incorrect registration of the same TRP, is also averted. Having said that, now it is time to show the TRP transfer process from the mouth to the models mounted on articulator. With the right provisional’s occlusal key (TRP) the left position is registered and vice versa, with the left provisional’s occlusal key the right position is registered (Fig. 7.19). Fig. 7.19 TRP registration technique by sectors for the assembly of master models.
Fig. 7.19A Registration of the incisal sector using the posterior intercuspation.
Fig. 7.19B Using the previously recorded anterior stop and the right provisional, the position on the left side is registered.
Fig. 7.19C Always keeping the anterior registration and the left provisional, the position on the right side is registered.
Fig. 7.19D Assembly in the dental practice of the lower master model to the upper one through the previously recorded keys.
To further increase the precision and to avoid losing posterior support, which could result in a sub-occluded registration, the provisional can be dissected to ensure support in the distal areas. Doing this is the more important, the more compromised the articular structures of the treated cases are. Then it will be the moment of the assembly on the articulator of the upper model, in arbitrary or individual hinge axis (Chap. 2). The assembly of the lower master model to the upper one and the cross-mounting with the provisional model have be carried out in the dental practice with their relative keys, with the patient on the chair, to be able to double check if everything perfectly interfaces (Fig. 7.20). In the case of implant rehabilitation, the provisional re-mounted on the master model will be used to assembly on articulator the models of the two arches; it must also be possible to remove the soft tissues from the master model for an adequate repositioning of the provisional. This technique is applicable in case of implant rehabilitation and has the advantage of not requiring the construction of registration keys. Of course, the procedure must be done in the dental practice with the patient waiting for the completion of the operating process and for the reintegration
into the mouth of the provisionals (Fig. 7.21). Fig. 7.20 TRP intraoral recording for the mounting on articulator of the master model interfaced to the provisional model (cross mounting).
Fig. 7.20A The figure shows the posterior keys’ detection (upper master, lower provisional) that were performed separately first on one side then on the other side, keeping the contralateral provisional.
Fig. 7.20B Assembly of the upper master model to the lower provisional model;at this point, also the assembly in ICP of the upper provisional model to the lower one will be granted. Fig. 7.21 Master-master mounting in case of implants, using the assembling technique of the provisional on the master model.
Fig. 7.21A Use of the upper and lower provisional to assemble the master models in TRP; the key in resin interposed to increase the accuracy of the mating is visible.
Fig. 7.21B The cross mounting is achieved by interfacing to the upper master model with the provisional inserted, the lower provisional model.
If, using the provisionals, all the registration keys will be carried out properly, it will be also easy to perform the cross-mounting between the master model and the provisionals’ model; the same therapeutic position of the oral cavity will have been reproduced in this way. The provisional model must strictly be with all removable teeth, because it is possible to have, in the final stage, the opportunity of improving certain aspects of the final work, without redoing an unnecessary new provisional and then copy it. The use of provisional models crossed with master models is crucial for the technician for what concerns the final management of the functional prosthetic space, since he/she will use a project tested into the mouth (therapeutic provisional), copied as regards volumes and spatial position. All the functional part will be revised and corrected in the light of the final parameters, evaluated after the re-education of the system.
Rehabilitative orthognathodontics with MEAW technique (Sato) In prosthesis and implant-prosthesis with wax-up it is possible to move the occlusal surfaces, creating a new occlusal relationship. In the same direction it is also oriented the orthodontics, which changes the natural teeth’s position and consequently their occlusal surfaces. Even in this branch of dentistry, the functional concepts accompanying the prosthetic rehabilitation will find an application. Orthodontics ensures the occlusion’s rehabilitation, it is therefore necessary to broaden its definition calling this discipline: rehabilitative orthognathodontics; it will be no longer considered as a mere pre-prosthetic treatment, but as an integral, often indispensable part of an interdisciplinary rehabilitation treatment. Through orthognathodontics natural teeth move and, therefore, the respective occlusal surfaces move; in prosthesis, occlusal surfaces are built with wax-up. So, even the orthodontics, in order to ensure the mandibular repositioning in TRP, must allow: the VD variation, the variation of the OP Inclination, the inclination’s management of the upper incisors and upper canines’ palatal surface, the management of functional arches. The technique that allows obtaining all these achievements is the MEAW (Multiloop Edgewise Arch Wire) technique, which is based on the Professor Sato’s philosophy (Figs. 7.22 to 7.26). Fig. 7.22 First phase of strategic leveling.
Fig. 7.22A Picture showing the strategic leveling technique on the lower arch. It ensures the molar axis’ straightening without losing the anterior anchor; it also allows regaining space in the anterior sector avoiding extractive approaches on premolars, correcting the inclination of the posterior OP.
Fig. 7.22B Strategic leveling on the lower arch; opening of the space between the first molar and the second molar as a result of the straightening of the second molar’s axis. Fig. 7.23 Elimination of posterior interferences through the MEAW arch.
Fig. 7.23A Right lateral view of a typical case of severe class II high-angle.
Fig. 7.23B Diagram showing the action of the tip-back given to the wire in the molar sector; it allows an OP inclination change (red arrow) intruding the lower molars more than the upper ones, thus eliminating the interferences given by the steepness of the posterior OP, favoring the mandibular advancement (blue arrow).
Fig. 7.23C Elimination of interferences in the molar area with OP flattening and the beginning of the anterior mandibular repositioning. Fig. 7.24 Mandibular position’s stabilization on premolars and reconstruction of class I intercuspation.
Fig. 7.24A Creating the steps on the MEAW arch between canine and premolar and through the action of a box elastic (yellow polygon) it is possible to act on the VD by extruding the premolars.
Fig. 7.24B Management of VD favoring the extrusion of the premolar area with box elastics, mostly in the upper arch (canine-premolar sectional wire); note the mandibular advancement and the stabilization of a class I relationship. Fig. 7.25 Final phase of the OP reconstruction and stabilization of the TRP.
Fig. 7.25A TRP stabilization acting on the upper premolar-molar area to favor intercuspation with the lower antagonist with flattened OP; note the mandibular repositioning and the articular compensation. The TRP stabilization is given by the function of the first premolars.
Fig. 7.25B Final occlusion in class I obtained through the mandibular repositioning. Note the new OP inclination, the upper first and second molar touch with their stamp cusps their antagonist fossae creating support and therefore stability; over time the upper molars will extrude improving the intercuspation.
Fig. 7.25C Pre-treatment macro-aesthetics; note the mandibular backward positioning and its negative effects on the facial macro aesthetics.
Fig. 7.25D Evidence of the mandibular repositioning effects on the macro-aesthetics of the face.
Fig. 7.26 Diagrams showing the action of MEAW by means of the effect of the intermaxillary elastics that are short on the OP inclination and on the resulting mandibular repositioning in classes II and III.
The cornerstones of this thinking are: • Strategic leveling of the arches; • elimination of the arch’s posterior interferences acting on the occlusal plane’s inclination; • elimination of interferences in the incisor and canine sector in order to facilitate the mandibular repositioning in sagittal and transversal directions; • stabilization of the mandibular position and of the VD by acting on the premolar area; • OP and occlusion’s reconstruction following Professor Slavicek’s functional parameters to stabilize the therapeutic position.
Early Mandibular Repositioning Technique (EMRT) From what explained above, the transversal application of the Vienna School’s therapeuticgnathologic concepts to all the rehabilitative branches of dentistry: orthodontics, prosthesis, implant-prosthesis, removable prosthesis, is even more evident. It has also been shown that the same concepts can be applied to all the dentition’s stages, from the full milk dentition to the adult edentulous; the clinician and his/her team will be able to always think in the same way (from 5 years old onwards) without changing rehabilitative and diagnostic concepts. The interceptive, preventive, early therapy, based on the VD and occlusal plane’s control, will functionally guide the mandibular growth and that of the entire maxillofacial complex. This type of therapy confirms the validity of Sato’s concepts about the genesis of malocclusions; early action on the VD, on the OP’s inclination, on the anteriorposterior position of the mandible and on the posterior discrepancy, allows to guide the mandibular growth according to functional principles, preventing the stabilization of occlusal disease and malocclusion (Fig. 5.9C). To demonstrate the effectiveness of this technique, a case of severe class II deep bite will be described, with therapy started at around 5 and a half years, late milk dentition, early mixed dentition. Once avoided the malocclusion’s stabilization and obtained a mandibular growth forward, the alignment of the upper and lower incisor area will be corrected by means of utility arches and class II elastics to be worn only during the night. Of course, for these cases
exactly the same diagnostic work-up is performed (Chap. 2), with the exception of the condylography and of the gnathologic chart (Figs. 7.27 to 7.31). When the final therapeutic position will be reached, with a class I dental relationship stabilized by a mandibular growth in anterior rotation, the patient will be regularly monitored. It will be appropriate to take action on the possible occurrence of the posterior discrepancy, to avoid a steepening of the OP which could cause a mandibular posterior rotation (relapse) because the patient is still in the growth phase. Any small corrections of the dental positions can also be executed with transparent masks. Once the growth will be completed, the case will be re-evaluated and possibly improved with a fixed therapy with MEAW technique. Fig. 7.27 Early Mandibular Repositioning Technique (EMRT).
Fig. 7.27A Pre-treatment situation: a full class II with severe deep bite in milk dentition is evident.
Fig. 7.27B Therapeutic position on the articulator, obtained by an increase of the VD of 4 mm on the incisal pin and a mandibular advancement of 3 mm up to the achievement of a class I relationship.
Fig. 7.27C Therapeutic position in the oral cavity, stabilized by overlay in composite applied to the upper arch in order to flatten the OP and favor an anterior mandibular rotation with condyle’s secondary growth and extrusion of the first permanent molars.
Fig. 7.28 Mixed dentition phase with first molars and incisors’ groups; note the deep bite’s disappearance and the stabilization of the molar relationship in class I.
Fig. 7.29 Change of the lateral sector. The utility arch allowed creating space for the teeth of the lateral sector and the alignment of the incisor sector. Note the molar and premolar key in class I. The class II elastics are worn only at night until the contact between the first premolars does not stabilize the occlusal relationship.
Fig. 7.30 Milk dentition change ending (complete eruption of permanent teeth).
Fig. 7.30A Left lateral view which shows the excellent occlusal relationship reached.
Fig. 7.30B After-treatment frontal view that highlights the impact of early mandibular repositioning on the control of a proper development of the mandible and of the occlusal relationship.
Fig. 7.31 Comparison between pre- and post-treatment LL x-rays, which highlights the mandibular growth in
anterior rotation with condylar secondary growth. Note also: • the flattening of the OP (red line); • the improvement of the soft tissues’ profile (green line); • the mandibular advancement demonstrated by the increase of the angle between S-N-PG (blue lines); • the mandibular angle’s closure (yellow lines).
The ten key points of the treatment plan Introduction The treatment plan must aim at achieving the ultimate goals that support the entire “rehabilitation journey”, both in patients with dysfunction and in those who are not affected by it. The goals are: • management of the functional prosthetic space; • mandibular repositioning; • reconstruction of the occlusion; • achieving functional aesthetic harmony. The attainment of these objectives will be implemented by following ten key points, listed and described below. 1. Removing the posterior discrepancy
Reminding Sato’s concepts related to the central role of the OP inclination in the genesis and correction of malocclusions, firstly it will be necessary to eliminate early, by means of a preventive approach, the posterior discrepancy. Its elimination is needed to manage the OP inclination both in orthodontics and in prosthesis. 2. Controlling the vertical dimension
VD will have to be checked to establish the baseline situation and to assess the achievement of the functional aesthetic result. 3. Creating posterior support
It will be essential to restore the occlusal surface at least up to the first molar, precisely to ensure that the molar sector fulfills the support function to which it is delegated. 4. Correlation between OP inclination and SCI
Knowing the SCI is of pivotal Importance so that, depending on the disclusion angle (DA) rule, the OP inclination can be related to it. In this way, in dynamics a minimum space between dental arches, without occlusal interferences and with the maximum masticatory efficiency, will be obtained (Fig. 8.1).
Fig. 8.1 Also in full denture the OP construction follows the same rules. 5. Sequential occlusion (Classes I, II, III and cross-bite)
In order to stabilize the mandibular position, a precise occlusal relationship is needed, which in orthodontics must aim at the class I dental relationship, but in prosthesis it can also be found in classes II and III. All class relationships can have, in the premolar-molar area, the cross-bite variant. Of course, all the three types of occlusal relationship will be constructed according to the concept of sequential occlusion with canine dominance. This Professor Slavicek’s concept includes the construction of a laterotrusive control over the first molar, second premolar, first premolar and on the canine, with increasing inclination up to the canine dominance. Obviously, the inclination values of the guides will be individual and will depend once again on those of the SCI (Figs. 8.2-8.4).
Fig. 8.2 Overview of sequential wax-up with canine dominance.
Fig. 8.3 Class II occlusal relationship; note the retrusive control and the protrusive guidance between the upper first premolar and the lower canine. Fig. 8.4 Class III relationship with left cross bite.
Fig. 8.4A In the occlusal relationship of class III in cross bite, the curves of active and passive centric are reversed, the first lower premolar indicates the reversal point.
Fig. 8.4B Right mediotrusion; note the canine dominance and the sequential disclusion. The F1-F2 guides are located on the lingual cusps’ slopes of the lower teeth, while the active centric is on the buccal cusps of the upper teeth. 6. Correlation between incisors and SCI, incisors’ control
As already said, the inclination of the long axis of the upper incisor is not a functional parameter sufficient to the management of the function, given that to a correct inclination of the axis may correspond a too steep or too flat inclination of its palatal surface (F1-F2 tract). Conversely, the inclination of the incisor’s palatal surface related to the SCI allows having an individual functional space and adequately managing the incisor sector, both aesthetically and functionally. In this way, the mandible will be able to move without putting in place harmful avoidance mechanisms (Fig. 8.5). Fig. 8.5 Upper incisor’s palatal surface.
Fig. 8.5A Functional structure of the upper incisor’s palatal surface.
Fig. 8.5B Protrusive movement, the horizontal blue line indicates the functional limit i.e. the F2 point, beyond which the aesthetics is created. 7. Correlation between canine and SCI, laterotrusive and protrusive control
Even in the mediotrusive movement led by the contralateral canine, in which also comes into play the whole palatal part of the incisor group, the rule that provides for the inclination of the canine’s palatal surface correlated with SCI is respected. In this way, only the muscles intended for a specific movement will come into action, avoiding activations in case of too steep or too flat inclinations of muscle groups that should be at rest during that specific movement. With the distal part of its palatal face, the canine intervenes with the first lower premolar in protrusive control (Fig. 8.6). Fig. 8.6 Upper canine’s palatal surface.
Fig. 8.6A Laterotrusive control of 13 in left mediotrusion; note that also the palatal surfaces of the upper incisors are protected and do not contact.
Fig. 8.6B The protrusive control creates posterior disclusion and protects the incisal sector (no-contact). 8. Correlation among molars, premolars and SCI
The same individual functional opening of the incisor and canine’s sector must be observed in the premolar and molar sector, always in accordance with the SCI. In the first molars’ occlusal relationship, the point of contact of type A between the vestibular part of the lower stamp cusps and the inner part of the upper cutting cusps has to be eliminated because it would produce a too closed upper arch, preventing a smooth mandibular movement on the laterotrusive side. To this aim, in this area a guidance surface from the F1 (upper passive centric) point to the functional point F2 will be created. The individual functional space in the anterior, lateral and posterior sectors of the arch will be used to manage the functional movement of the mandible without interference. Often the disapplication of this concept leads to prosthetic crowns’ fracture problems (buccal cusps of upper molars and premolars) or to wear facets due to iatrogenic parafunction (Fig. 8.7).
Fig. 8.7 Diagram of the laterotrusive guidance on the first molar; note the opening of the upper buccal cusps. 9. Retrusive control of the first molar
In the transition from milk to mixed dentition, the eruption of the first molar and the relationship that is established between the upper and the lower molar is the occlusion key in a class I relationship. In particular, the occlusal anatomy of the first molars performs the retrusive control: mainly the transverse ridge of the upper molar, with its mesial side, acts against the distal side of the distal-buccal cusp of the lower molar. This molar retrusive control is a pivotal function for the stabilization of the mandible forward. 10. Retrusive control, protrusive guidance and protrusive control of the upper and lower first premolars
The eruption of the first premolars creates a more anterior key that, especially in rehabilitations with mandibular repositioning, plays a key role in retrusive control (disclosing the posterior sectors). In protrusion, this key guides the mandible in reaching the ICP created in the new therapeutic position. In classes II, this function is performed by the first upper premolar and by the lower canine. From the ICP, moving forward, the first lower premolar intervenes together with the upper canine in protrusive control (Fig. 8.8).
Fig. 8.8 Relationships between the first lower premolar and the upper canine in order to carry out the protrusive control; relationship between the first lower premolar and first upper premolar for the dual function of protrusive guidance and retrusive control.
All the four treatment goals listed at the beginning of this short chapter can be reached and can resolve the pathology of the case and avoid creating iatrogenic diseases only if the ten points listed above find a strict application. Applying these points will stake a claim on the long-term stability of the therapy, as regards the prosthetic device, the resolution of symptoms and the functional aesthetic harmony of the face. Finally, all the data related to the project will be kept, ensuring in this way the possibility of checking the functionality over time. The Brux Checker appears therefore as an indispensable tool for controlling the created occlusion and for being able to monitor it in time, intercepting in advance the appearance of parafunction (Figs. 8.9-8.10).
Fig. 8.9 Sequential wax-up with canine dominance, with a right class I relationship and a left middle-class II relationship. The entity and the inclination of the functional space located between the passive centric and the functional aesthetic arches are evident; this functional space is an essential parameter for proper mandibular dynamics. Fig. 8.10 Functional guides.
Fig. 8.10A Functional guides’ inclination from the first upper molar to the incisors in a post-orthodontic treatment mouth.
Fig. 8.10B Complete reconstruction on implants; note the inclination of the functional guides built according to the sequential occlusion concepts with canine dominance.
CASE REPORT 1
Clinical Case Studies Introduction In what follows are presented three clinical cases that share the variation in vertical dimension (VD), that is to say, the three-dimensional repositioning of the mandible following the concepts illustrated in this book. The treatment plans provided a multidisciplinary approach with the use of rehabilitative orthodontics with MEAW technique (case 2 and Fig. 7.23). Of course the most important stages of the therapeutic path will be explained, from the diagnosis to the implementation of the treatment plan. Each case will be introduced by means of a diagnostic and therapeutic framework’s description.
CASE N° 1 (2006)
Variation in vertical dimension and implant-prosthetic rehabilitation in a Class III case.
55 years-old male patient, smoker, with severe dysfunctional problems resulting from missing teeth, collapse of the occlusion and mandibular displacement (left MLD). Clinically, the lack of posterior support and significant abrasions of the residual teeth in the anterior part of the arch are detected (caused by an anterior chewing and by serious dysfunctional problems such as clenching and daily and night bruxism). In a relaxed position, with separate arches, the edges of the upper and lower incisors are not visible. There is a strong pain component borne by the neck, and an altered posture of the head; sleep apneas are detected. Despite a VD value of 46.8°, slightly higher than the standard, an ODI of 75.7° indicating a tendency to a high vertical dimension, the treatment plan provided for an increase of the VD of 4 mm on the incisal pin. This decision was necessary for incisors’ reconstructive aesthetic reasons and to avoid recreating a deep bite. The electronic condylography shows a SCI value of 38.2°, therefore tending to be flat; to have a disclusion angle of about 8°, the OP will be 6° with a cusps’ angle of 25°, to prevent posterior interferences. The treatment plan envisaged a mixed rehabilitation on implants and natural teeth, and direct composite restorations, minimally invasive, on natural elements without prostheses. Prosthetic structures made in zirconia with layered ceramic have been used, together with others structures in classic metal ceramic. In accordance with the principles governing the gnathologically-guided implant positioning, horizontal deficits of the bone were treated with split-crest (ERE) using the ultrasonic surgical technique; the sinus’ lifting in area 15 was carried out with Dr. Bruschi’s Localized Management Sinus Floor (LMSF) technique, which provides for the management of the palatal bone wall of the maxillary sinus. The reconstruction of the sector 33-43 was carried out with composite veneers, without dental preparation. The 12-11-21 elements have been retreated from the endodontic point of view and reconstructed in composite with glass fiber posts. A slightly subgingival prosthetic preparation was made, in order to obtain the cerclage effect and to avoid a more invasive surgical treatment of lengthening of the clinical crown. The management of the provisional with the reassembling technique (functional part) allowed managing in an excellent way the mandibular repositioning acting on the occlusal surface; the same management has also allowed the conditioning of soft tissues (biological part) on natural teeth and implants. The post-treatment repetition of the initial records showed a return to normality (in line with the skeletal type of the patient) of all the parameters that in the pre-therapeutic phase were altered. Fig. 1 Pre-treatment facial macro-aesthetics in ICP.
Fig. 1A Frontal.
Fig. 1B Lateral. Fig. 2 Intraoral view of dental arches in ICP.
Fig. 2A Right lateral view.
Fig. 2B Frontal view.
Fig. 2C Left lateral view.
Fig. 2D Upper arch.
Fig. 2E Lower arch.
Fig. 3 Cephalometric tracing according to Slavicek: it highlights the value of the vertical dimension, equal to 46.8° (green value), the occlusal plane’s inclination and the skeletal class; this is a class III case, tending to I, with a normal VD.
Fig. 4 Condylographic tracing of protrusion and retrusion: the exam highlights the eminence’s inclination (flat), Bennett, and dysfunctional problems with left delta Y. The functional parameters’ value showed a SCI of 38.2° (flat). Fig. 5 Gnathologically-guided implant placement.
Fig. 5A Surgical phase in area 13 (ERE) -15 (LMSF).
Fig. 5B Split-crest in the 34-36 sector.
Fig. 5C Split-crest in area 46.
Fig. 5D Manual preparation of the implant site in area 44. Fig. 6 VD increasing of 4 mm according to Slavicek’s philosophy and remounting on articulator in the new position.
Fig. 6A After having mounted the models in ICP, the incisal pin is risen by +4 mm and a registration wax, 4 mm thick, is built with lower incisors’ reference indentations to control the mandibular position during the TRP registration inside the mouth.
Fig. 6B Registration in the mouth of the new TRP position, set to +4 mm.
Fig. 6C View of models in therapeutic position (+4 mm) ready for wax-up, preparatory for the construction of the therapeutic provisional.
Fig. 7 Functional mock-up: assessment of the lower incisor edge’s position, which identifies the anterior point of the gnathologic occlusal plane.
Fig. 8 Sequential wax-up for the execution of the therapeutic provisional: the occlusal plane’s accessory position with inclination of 6°, using the functional mock-up to define the OP anterior point. Fig. 9 Wax-up in therapeutic position performed according to the sequential philosophy with canine dominance (Slavicek).
Fig. 9A Right lateral view.
Fig. 9B Angled view that shows the sequential concepts, the class I relationship and the functional space’s width.
Fig. 9C Upper wax-up, in blue the protrusive control over the canine’s distal fossa.
Fig. 10 Cross mounting of the wax-up and of its plaster’s duplicate to be used for the provisional’s construction.
Fig. 11 Therapeutic provisional in TRP: note the occlusal class I relationship, in compliance with the initial wax-up design. Fig. 12 Provisional’s assembly in the mouth with appropriate reference keys not to lose VD and occlusal plane’s inclination.
Fig. 12A The provisional is positioned before the lower right area (provisional screwed on implants against natural teeth) obtaining the stabilization of the therapeutic position.
Fig. 12B Provisional’s positioning, screwed on implants in sector 4; recess of the cemented provisional on implants and natural teeth in sector 1. Fig. 13 Therapeutic provisional, on implants (screwed) and natural teeth, and composite veneers in the 4333 sector.
Fig. 13A Right lateral view.
Fig. 13B Frontal view of the new VD.
Fig. 13C Facial macro-aesthetics of the patient after the functional prosthetic space’s reorganization through the therapeutic provisional. Fig. 14 Reassembly of the therapeutic provisional according to the OMRT technique (Bassetti).
Fig. 14A Upper provisional’s impression; the same process is performed for the lower arch.
Fig. 14B Models with provisionals mounted on articulator in reference position RP.
Fig. 14C View of the occlusal relationships seen from behind: in RP position the midline is re-centered with a displacement of the mandible to the right, the posterior support is restored with composite acting on the lower provisionals only.
Fig. 15 Intraoral view of provisionals in the final therapeutic position: note the re-centering of the midline.
Fig. 16 Definitive impression.
Fig. 16A Preparation of the maxilla for the final impression with the double tray technique that allows managing precisely implants and natural teeth; the same process is performed in the lower jaw.
Fig. 16B Upper silicone’s impression, with the plaster impression of the implants incorporated on. Fig. 17 Recognition of relations between the two arches (TRP) using the provisional’s position.
Fig. 17A Left registration with the right provisional.
Fig. 17B Right registration with the left provisional.
Fig. 17C Master models assembled on the articulator in therapeutic position.
Fig. 18 Data necessary to the laboratory for the individual setting of the articulator. Fig. 19 Sequential wax-up with canine dominance.
Fig. 19A Setting of the lower active centric through the occlusal plane’s accessory.
Fig. 19B Functional structure of the upper arch and pattern of sequential guides. Fig. 20 View of the final restoration on the articulator.
Fig. 20A Details of the occlusal relationship on the buccal side; from this angle the protrusive and retrusive controls, and the anterior and lateral functional space are clearly visible.
Fig. 20B Detail of the protrusive control (right) between the lower premolar and the distal fossa of the upper canine seen from the inner side: note the no-contact of the incisors, obviously, on both sides. Fig. 21 Intraoral view of the final restoration.
Fig. 21A Right lateral view.
Fig. 21B Frontal view.
Fig. 21C Left lateral view.
Fig. 21D Upper arch; note the width of the functional arches.
Fig. 21E Lower arch; note the width and symmetry of the active centric arch.
Fig. 22 Post-treatment facial macro-aesthetics: to detect, the relaxation of the facial mimic muscles and the improved postural attitude of the head.
Fig. 23 Detail of the retrusive control - protrusive guidance in TRP among the first upper and lower premolars: note the first contact at the level of the first premolars and disclusion in other sectors. Fig. 24 Functional movements.
Fig. 24A Protrusion in frontal view; note the protrusive control’s function that prevents excessive contact of the incisors.
Fig. 24B Left mediotrusion in the right lateral view; note the sequential disclusion.
Fig. 25 Brux Checker to test the final occlusion during sleep and night parafunctions: the patient still presents strong bruxism as evidenced by the extension of the white areas. As indicated by the arrows the
mediotrusive controls on upper canines (blue arrows), the retrusive controls (yellow arrows) on the first premolars and on the transverse ridge of the upper first molar, and the protrusive control (green arrow) on the distal slope of the upper canine, are able to control the parafunction. Fig. 26 Health status of soft tissues.
Fig. 26A Health status of the tissues around the implants.
Fig. 26B Health status of the tissues around the natural teeth.
Fig. 26C Functional aesthetic integration in the upper incisor area.
Fig. 27 Functional prosthetic space evaluated on the LL x-ray of the skull, pre- and post-treatment: notice the difference of contraction at the level of perilabial soft tissues, the new position of the hyoid bone and the mandibular repositioning towards a skeletal class I.
Fig. 28 AP x-ray of the skull, pre- and post-treatment: note the return to symmetry on all the spatial planes, especially the re-centering of the mandibular position.
CASE REPORT 2
CASE N° 2 (2004)
Class II case: low angle treated with an orthodontic-implant-prosthetic multidisciplinary approach
The case describes the therapeutic treatment developed on a female patient of 43 years-old, with a severe dysfunctional framework, whose symptoms were: muscular tension headaches (anterior temporal area), clicking of the left and right joints resulting in pain, neck pain, clenching and day and night bruxism, evident abrasions of the residual tooth structure. The patient reported to find relief only through advanced mandibular position with incisors almost edge-toedge, inserting the tongue into the space that opens up between the dental arches. The early loss of 36-3746 in the lower arch had caused a narrowing of the edentulous space, with strong inclination of the posterior occlusal plane, which had also produced a mandibular backward positioning, also compounded by the evident deep bite. This situation has led to an altered condyle-meniscus relationship, with articular clicking, pain and postural problems. The clinical analysis through muscle palpation showed a strong muscular impairment: the occlusal index had a value of 2.5, it appeared very high. After the initial diagnostic process, the treatment plan envisaged a pre-treatment with splint to solve the painful symptoms and to test the future therapeutic position. Later, it moved to the orthodontic treatment with MEAW technique to re-open the spaces for the missing teeth and to reposition the mandible by increasing the vertical dimension. Finally, through the therapeutic provisionals and the reassembling technique, the therapeutic position for the finalization of the case has been defined, with bridges in zirconia-ceramic on the lower arch, an implant in position 26 and direct composite restorations of the abraded tooth surfaces. Fig.1 Pre-treatment facial macro-aesthetics in ICP.
Fig. 1A Lateral view.
Fig. 1B Frontal view. Fig. 2 Pre-treatment intraoral pictures.
Fig. 2A Right lateral view.
Fig. 2B Frontal: note the complete coverage of the lower incisors by the upper ones in ICP.
Fig. 2C Lateral left.
Fig. 3 Initial pictures of models mounted on articulator in right lateral view: the deep bite, the dental class II relationship, the lack of space for the missing teeth, the remarkable steepness of the posterior occlusal
plane and the teeth wearing are even more visible. The same features are found on the opposite side.
Fig. 4 LL x-ray of the skull that highlights the postural aspect of the head, which is a consequence of the occlusal plan’s steepness, which causes a mandibular backward positioning. This situation, in addition to the issues related to the TMJ, causes a narrowing of the upper airways (green arrow), with consequent rotation of the head, upward and backward, as well as negative effects in the cervical area of the column. The data from the cephalometric tracings according to Slavicek-Sato, confirm a class II with facial height lower than 41.3° (low angle).
Fig. 5 Protrusion-retrusion condylographic tracing: it shows a significant alteration of quantity, characteristics, quality and symmetry; furthermore, there is a delta Y to the right side (red circle). Since the right and left average value of SCI is 49°, in order to have a disclusion angle of about 9°, the OP inclination should be of 10°.
Fig. 6 Ortho-panoramic radiography confirms what seen clinically, namely the lack of 26-36-37-46 and a severe mesial inclination of 27-38-47-48, with notable lack of adequate space to replace the missing teeth. Red arrows and dashed yellow lines indicate the need for correcting the dental axis in order to re-open the space for missing teeth. The treatment plan explained to the patient, provides conventional prostheses in the 3rd and 4th quadrants and a rehabilitation with implant in position 26.
Fig. 7 RP position identifiable with the initial therapeutic position TRP. To note, the tendency of the mandible to reposition itself anteriorly, with opening of a posterior space to be filled in order to stabilize the anterior position of the mandible. Finally, the posterior interference is highlighted (red arrow to the right in zone 48) due to the steep occlusal plane, which hinders a further mandibular advancement.
Fig. 8 Initial pre-treatment with splint in TRP positon. The resin thickness in the lateral zones is useful to eliminate the posterior interferences and the deep bite, keeping the patient’s ideal VD.
Fig. 9 Orthodontic therapy in the ending phase of upper and lower arches’ strategic leveling: the spaces for the missing teeth re-open, decreasing the OP inclination in the posterior sector. Fig. 10 Intermediate phase of the treatment with MEAW arch.
Fig. 10A Right lateral view; there are clear step-up bends on premolars to increase the vertical dimension by means of the action of box elastics.
Fig. 10B Left lateral view; there are clear step-up bends on premolars to increase the vertical dimension by means of the action of box elastics.
Fig. 10C Occlusal view of the lower arch: note the correct re-opening of the spaces, which allows to insert the therapeutic provisionals in the lower posterior sectors, right and left. In the maxilla, the reopening of the
space allows the insertion of the implant on the 26 with its provisional crown. Fig. 11 Therapeutic provisional.
Fig. 11A-B Phase of the therapeutic provisional, respectively 11A in right lateral view and 11B in left lateral view. At this stage it is possible to obtain a further increase in vertical dimension making use of the provisionals and continuing with the orthodontic therapy that, through the action of the elastics, promotes the extrusion of the upper and lower premolars up to bring them in occlusion with the lower provisional. The provisional on the implant of the 16 allows to have a secure support in vertical direction and to maintain the spaces in the mesio-distal direction.
Fig. 12 Reassembling on the articulator of provisionals in RP. Right view: once the recording wax is removed, at first contact the lack of posterior support to the right and to the left is highlighted and a MLD toward the left side (also detectable in the mouth) is visible. It has been decided to increase the vertical dimension of 2 mm on the incisal pin (changing then the provisionals) and to recenter the midline by moving the mandible of 2 mm to the right.
Fig. 13 New therapeutic position. W ith the composite, the lack of posterior support on the provisional to the right and to the left is compensated, adapting the new occlusal plane of provisionals to that of the upper arch. Fig. 14 Intraoral vision of the new therapeutic position (TRP). Following the changes made on the provisional, the re-centering of the midline is obtained, with a dental class I relationship, both to the right and to the left. In the anterior sector there is the space needed for the reconstruction of the lower incisors’ incisal edges. Note the ideal relationship of the lower first premolar with the upper first premolar and with the canine, helpful for the stabilization of the mandibular position.
Fig. 14A Right lateral view. The same situation occurs on the left side.
Fig. 14B Frontal view with re-centering of the midline and resolution of the deep bite as a result of the VD increase. Fig. 15 The resulting vertical dimension allows having the right space for the direct reconstruction in composite of lower incisors’ edges.
Fig. 15A Direct reconstruction under dam with the aid of a mask derived by the wax-up.
Fig. 15B Frontal view of the lower incisors edges’ reconstructions. In the upper incisor area diastemas are still present, which can be closed with the composite through direct additive techniques. Fig. 16 Finalization of the treatment. The therapeutic position is stable and asymptomatic: proceeding to the case finalization.
Fig. 16A Lower master model with registration of the therapeutic position carried out in the mouth with the technique by sectors; the registration keys in resin are rebased with temporary cement.
Fig. 16B Mounting on the articulator of the lower master model in the same therapeutic position of the provisional. Following the programmatic condylographic examination, the necessary data are sent to the laboratory for the individual setting of the articulator.
Fig. 17 Posterior view of zirconia structures, from which you notice the perfect match between the upper stamp cusps and the lower fossae (and vice versa), respecting the concepts of functional arches, that is to say active and passive centrics. Fig.18 Finished prosthetic devices on the master model.
Fig. 18A Obtaining of an adequate occlusal anatomy, built around the functional structure of the tooth.
Fig. 18B Canine dominance in the right mediotrusion (left laterality).
Fig. 18C Sequential guide’s concept: in the right mediotrusion, in the absence of the canine, the first premolar discloses the teeth distal to it. Fig. 19 Status of health of the soft tissues around the implant: it is obtainable through implant insertion preceded by an increase of hard tissues with split-crest and with a proper management of the cervical part (biological part) of the provisional.
Fig. 19A Health status of the soft tissue around the implant.
Fig. 19B Integration of soft tissues’ profile around the crown. Fig. 20 Intraoral view of the final restoration.
Fig. 20A Right lateral view: notice the class I dental relationship.
Fig. 20B Frontal: notice the centered midline, the elimination of the deep bite and the closure of the upper diastemas with additive techniques, which help to keep an adequate width of the arch.
Fig. 20C Left lateral view: notice the class I dental relationship.
Fig. 20D Upper arch: note the retrusive control on the crown of the 26 and the direct reconstruction of the 16.
Fig. 20E Over-jet and over-bite: note the restoration of a functional space correlated with the SCI.
Fig. 20F Lower arch: note the correct symmetry or the active centric arch and the direct restorations in composite of the wear incisal edges of the incisors and of the canines and first premolars’ cusps. Fig. 21 Overview of occlusal relationships in ICP: intraoral pictures with 45° viewing from the bottom that allows seeing the relationships between the lower active centric and the upper passive centric and the occlusal controls at molar and first premolars level.
Fig. 21A Right view: the retrusive controls on the first premolars, upper and lower, and on the transverse ridge of the upper first molar are very well visible.
Fig. 21B Left view: the retrusive controls on the first premolars, upper and lower, and on the transverse ridge of the upper first molar are very well visible.
Fig. 22 Final Brux Checker to test the built occlusal schemes and their ability to control the parafunction. The yellow arrows show the retrusive controls on the mesial part of the upper first molars’ palatal cusp and on the transverse ridge of the upper first molars; blue arrows show the canines’ laterotrusive control.
Fig. 23 Post-treatment aesthetics.
Fig. 23A Facial macro-aesthetics after the three-dimensional mandibular repositioning.
Fig. 23B Smile mini-aesthetics (lips and teeth) in frontal view.
Fig. 23C Smile mini-aesthetics (lips and teeth) during phonation in lateral view.
Fig. 24 Post-treatment sagittal and frontal radiographic view. The LL radiography (left picture) shows the variation of the VD, the OP new orientation, the new interincisal angle, the restoration of airways’ width, and the re-establishment of the aesthetic parameters: nasolabial angle and Ricketts’ aesthetic line. The posttreatment AP radiography (right picture) shows the correct restoration of VD and of symmetries on the frontal plane.
Fig. 25 The left ortho-panoramic post-therapy radiographic examination highlights the correct re-opening of spaces for restoring the missing teeth and the straightening of 27-38-47 axes.
Fig. 26 Overlapping of condylographic tracings of protrusion and retrusion, pre-treatment (blue) and posttreatment (green). The return to the standard of all the parameters (quality, quantity, characteristics and symmetry) has to be highlighted, with disappearance of the initial deviation to the right side (delta Y), thus with recovery of the movement’s symmetry.
CASE REPORT 3
CASE N° 3 (2007)
VD variation in an implant-prosthetic case of Class III low angle.
The patient, a woman of 40 years-old, had dysfunctional symptoms with articular noises, neck pain, headache, clenching and bruxism; symptoms confirmed by the initial diagnostic process. The skeletal type led back to a Class III (APDI 95) low angle (ODI 63). The treatment plan, for therapeuticand rehabilitative purposes, provided for a variation of VD with consequent mandibular repositioning through the management of a therapeutic provisional and an implant-prosthetic rehabilitation. After the extraction of irrecoverable teeth in the 1st and 4th quadrants, connective grafts taken from the palate were effectuated, in order to increase the keratinized mucosa in the 3rd and 4th quadrants. Bone volume in vertical and horizontal directions had to be increased using bone grafts taken from the mandibular ramus on the 3rd and 4th quadrants’ area. 4 months after, the implants were inserted. In zone 16, a maxillary sinus’ lifting was made, passing by the crest. After three months, the first provisional was put in its habitual position, regaining the necessary posterior support. At this point, it has been possible to manage a vertical dimension’s variation of 6 mm, obtained in two distinct phases, increasing it of 3 mm each time (OMRT). The successive stages of reassembly on the articulator of the therapeutic provisional led to the final mandibular position, repeatable and asymptomatic, used to finalize the case. The VD variation and the consequent mandibular repositioning allowed recreating an appropriate functional prosthetic space for a functionally correct management of the OP and of the teeth’s spatial position. This ensured the aesthetic result and the resolution of the painful symptoms linked to dysfunction. Fig.1 Pre-treatment facial picture.
Fig. 1A Lateral view that shows the effects of a low VD on the lips’ contour.
Fig. 1B Frontal view with a smile that highlights the overtone of the whole facial mimic muscles. Fig. 2 Intraoral view.
Fig. 2A Right Lateral: note the OP’s shape.
Fig. 2B Frontal: there is a midline deviation to the right.
Fig. 2C Left Lateral: clear lack of posterior support.
Fig. 2D Upper occlusal view.
Fig. 2E Lower occlusal view: note the volumetric deficit borne by the edentulous saddle. Fig. 3 Variation iter of the VD.
Fig. 3A The values inside the red box refer: above (43.8°), to the situation in ICP, below (45.2°) to the ideal VD value. Inside the yellow box there are the values of the first step of VD variation (+3 mm) corresponding to 45.3° of lower facial height. Finally, in the green box, the final VD variation of +6 mm is indicated, corresponding to a lower facial height of 46.6° (therapeutic VD).
Fig. 3B Diagram of VD values; the blue line indicates the starting point, which is slightly lower than the ideal value of VD; the red cross indicates the increased value (+6 mm); despite being a value greater than the ideal one, it always remains within the green zone.
Fig. 4 Protrusion-retrusion condylographic tracing; it shows a slight deviation of the movement toward the left side, a reduced quantity of the right tracing compared to the left tracing, and finally a steep eminence, if compared to a SCI value of 52°. Fig. 5 Lower arch preparation for the implants’ insertion.
Fig. 5A Lower arch after connective tissue grafts, made in order to increase the soft tissue’s thickness. Subsequently, the bone grafts taken from the mandibular ramus will be performed, in order to increase the vertical and horizontal bone volumes.
Fig. 5B Surgical mask made with the sectioned model technique; note the lingual inclinations of the implants’ axis in the first molar position.
Fig. 5C Lower arch after the implants’ insertion and tissue conditioning with the provisional; to note, the health status of the peri-implant tissues, a result of the soft and hard tissue’s increases previously made.
Fig. 6 First provisional in ICP, without varying the VD, to restore the posterior support, correct the OP
inclination and perform the re-mounting technique of the therapeutic provisional. Fig. 7 VD registration to +3 mm for the first provisional.
Fig. 7A Functional aesthetic Mock-up (direct) of the incisors to +3 mm; note the lower incisor position, 1.5-2 mm beyond the lower lip (which is the anterior reference point for defining the OP inclination).
Fig. 7B Position inside the mouth with a stop on the incisors to +3 mm; in the posterior space the wax to record the new therapeutic position will be positioned, wax that will be used to remount the provisionals on the articulator (remounting technique of the therapeutic provisional).
Fig. 7C Remounting of the provisional models in the new TRP and lower arch’s wax-up.
Fig. 7D Lower provisional’s modification by means of the mask obtained from the previous wax-up. Fig. 8 Positioning in the mouth of the provisionals in the new VD (+3 mm).
Fig. 8A Positioning of the modified provisionals; note the space that has been created in the incisal sector, it is useful to manage properly the aesthetic and the function.
Fig. 8B Completion of the upper provisionals and bonding of composite overlay on the lower incisors and canines. Fig. 9 TRP re-evaluation and further VD increase of +3 mm (OMRT).
Fig. 9A Remounting in RP of the provisionals’ models; in the new position there is a posterior space that corresponds to a +3 mm of increment on the incisal pin.
Fig. 9B Remounting of the provisionals’ models to the new position recorded in the mouth at +3 mm. As can be seen from figure 9A the space between the arches will be filled with the reintegration (made in composite) borne by the upper provisionals adapted to the lower OP.
Fig. 10 Therapeutic provisional in the final therapeutic position (+6 mm in total). Movement of left mediotrusion, made possible following the provisional restoration of canines’ laterotrusive control; this is crucial to ensure that the provisional can perform its function of system’s reeducation. Fig. 11 Final impression and mounting on the articulator in TRP.
Fig. 11A Upper arch’s preparation for the final impression (implants and natural teeth). The same procedure will be implemented on the lower arch.
Fig. 11B Registration of the TRP with the technique by sectors through the provisionals; the picture shows how the left provisional freezes the TRP position to record on the right (the same operating path will be made on the opposite side).
Fig. 11C Master models assembled on the articulator in the TRP position, recorded by the resin keys.
Fig. 11D Cross mounting of the upper master model with the lower provisional model, through the resin keys registered into the mouth (always using the technique by sectors).
Fig. 12 Sequential wax-up with canine dominance.
Fig. 12A Wax-up of the lower arch with the OP inclination equal to 10°.
Fig. 12B View from the bottom of the wax-up before it is refinished; the red arrow indicates the retrusive control on the upper first molar transverse ridge; the green arrow indicates the protrusive control over the upper canine distal fossa and the yellow arrow indicates the functional space between the upper and lower incisors, space needed for a proper mandibular dynamics. Fig. 13 From the wax-up to the final prosthetic device in accordance with the initial project.
Fig. 13A Structures in zirconia (right side): see how a correct VD allows creating structures with adequate thickness.
Fig. 13B Definitive prosthesis on the model (right side): see the excellent class I dental relationship, made possible by a correct positioning of the implants, in compliance with an appropriate mandibular repositioning.
Fig. 13C Inner view of the right side with evidence of a class I dental relationship from the canine to the molar; note also the protrusive guide and the retrusive control between the upper and lower first premolars (red arrow). Fig. 14 Crowns made of lithium disilicate on 13-23: it will be possible to readjust the anatomy of the canine from an aesthetic and functional point of view.
Fig. 14A Detail of the lithium disilicate crowns.
Fig. 14B Note the minimally invasive approach on 23, ready for the adhesive cementation of the crown (same thing for the element 13). Fig. 15 Details of the prostheses.
Fig. 15A Upper incisor Group.
Fig. 15B Elements 35 and 36; the correct handling of the VD allows the recovery of the anatomy, with adequate thickness of the ceramic materials. Fig. 16 Intraoral view of the final implant-prosthetic rehabilitation.
Fig. 16A Right lateral view with class I occlusal relationships.
Fig. 16B Frontal view with centered midline and adequate dental proportions.
Fig. 16C Left lateral view with class I occlusal relationships.
Fig. 16D Upper arch: to note, the width of the arch and the inclination of the palatal surfaces of the upper incisors and canines in perfect correlation with the articular eminence inclination (according to Slavicek’s philosophy).
Fig. 16E Lower arch congruous with the upper one and adequate lingual space in the transversal direction.
Fig. 17 Protrusive control: this function, performed by the upper canine and by the lower first premolar, unloads the incisal sector during the protrusion movement, preserving over time the composite restorations on the lower incisors and canines.
Fig. 18 The Brux Checker at the end of the therapy shows how the occlusal concepts included in the reconstruction of the occlusal surfaces are able to explicate their control function on parafunctions.
Fig. 19 The final cephalometric tracing highlights the mandibular repositioning with transition from a class III to a class I with a slight tendency to class III. Also notice the reorganization of the aesthetic profile even if the mandible has a very pronounced anterior edge of the symphysis. Fig. 20 Facial macro-aesthetics.
Fig. 20A Frontal view with smile.
Fig. 20B Lateral view with smile. In both the shots, note the restoration of the facial symmetry in the three spatial planes and the significant relaxation of the mimic muscles compared to the initial situation (Fig. 1B).
Fig. 20C Functional aesthetic integration of the upper incisors; the position of their incisal edge is dictated by the function and the aesthetics is a consequence. Fig. 21 Control after 8 years, with stability of the aesthetic and functional result.
Fig. 21A Frontal view of the VD restoration and good management of the functional prosthetic space.
Fig. 21B Peri-labial mini-aesthetics in frontal view, a result of a correct positioning of the incisors in the functional prosthetic space.
Fig. 21C Peri-labial mini-aesthetics in lateral view; the upper incisor functional position allows an adequate mandibular movement, also during phonation.
Fig. 21D Micro-aesthetics and excellent integration of the restorative materials with gingival tissues.
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