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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

Functional Occlusion for the Orthodontist Part II RONALD H. ROTH, DDS DONALD A. ROLFS, DDS

The Repositioning Splint In our opinion, the two greatest causes of failure of occlusal treatment are: 1. Failure to stabilize and then capture true centric relation prior to occlusal therapy. 2. Failure to alter the occlusion with a high enough degree of precision to hold centric and still clear on movement. The purpose of the repositioning splint is to enable the operator to find "true" centric (which is stable and comfortable); to test the patient's response to change in the occlusion, prior to embarking upon a complex course of occlusal therapy; and, finally, to see if the mandibular centric relation position can be stabilized. Without the use of the splint, finding centric in the first place is usually not possible. Eugene Dyer popularized the use of the repositioning splint, which he now calls a craniomandibular orthopedic appliance. Dyer also pointed out a number of years ago that, in centric relation, the condyles are usually in the superior-anterior portion of the fossae. The splint is used whenever a patient is symptomatic and/or when the mandible is difficult to manipulate or, better yet, when the mandible is not easy to manipulate. Initially, splint treatment is directed toward alleviation of pain-dysfunction symptoms and the diagnosis of the true maxillomandibular relationship. The splint is a means of relaxing the mandibular musculature and resolving the inflammatory changes within the joint capsules. It also allows remodeling of the joints to occur, if there have been some previous degenerative changes. Only in this last respect is the splint not an entirely reversible therapeutic procedure. It tests the patient's response to occlusal change without actually changing the occlusion; and allows the operator to know if the mandibular position can be stabilized, and what the exact extent of the discrepancy is that must be corrected. It puts the patient to the test in terms of his or her desire to undergo complex occlusal therapy. It also allows the patient to know what he might expect, in terms of comfort, if the complete correction of the occlusion is undertaken. It is true that on a relatively asymptomatic patient a clever operator can obtain a repeatable limit position of the mandible that one could refer to as centric relation position. The issue is— "Would that position remain stable if the patient's occlusion were altered to make the teeth intercusp with the mandible in that position?" It has been shown that, through the use of a repositioning splint, most patients will reposition from the first clinically captured centric relation position. The greater the degree of pain or discomfort, the greater the amount of repositioning that usually occurs. Even those individuals that are relatively asymptomatic will reposition slightly from the first capturable centric

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relation position. It would appear that it takes some time for all muscle contracture and mandibular posturing to subside, and for any excess fluid in the joint capsules to resolve. Assuming no degenerative joint changes or bony recontouring are occurring, it is possible to stabilize the mandibular position so that a reproducible centric relation can be obtained from day to day or from month to month or even year to year on a nongrowing patient. Some clinicians who are opposed to the use of a repositioning splint have indicated that the splint itself may be the cause of the repositioning effect. This would have to be disputed on the premise that if this were so, then it should be impossible to stabilize any patient on the repositioning splint. Those whom we cannot stabilize with the repositioning appliance are a small minority, who usually have radiographic signs of degenerative or bony recontouring processes going on. The overwhelming majority of patients are stabilized and their symptoms eliminated. It is of interest that there are a number of patients, who are devoid of pain or discomfort, who reposition a considerable amount from the first capturable centric position. These are usually patients who have other signs of occlusal disharmony, aside from pain-dysfunction symptoms. Missing this type of discrepancy could result in a misdiagnosis and an inappropriate treatment plan that may result in postorthodontic TMJ problems. It must be made clear that we simply cannot believe what we see in the patient's mouth in regard to occlusion and centric relation. The patient will always close in a manner to gain intercusping of the teeth. The neuromuscular protective mechanism will cause him to accommodate his jaw position to the intercusping of the teeth. The purpose of an anatomical articulator is to eliminate the patient's neuromuscular response to his existing occlusion, so that we may see how his teeth relate when the jaw joints are properly related to the fossae. This is the basis for occlusal therapy and TMJ treatment. It is the cornerstone of functional occlusion concepts. The teeth should not interfere with proper condyle relationship with the fossae either upon closure or movement. Because of the patient's neuromuscular protective mechanism and proprioceptive sense, we can never trust the "bite" that the patient exhibits intraorally or we will be fooled in a very high percentage of cases. Unmasking the Discrepancy In the treatment of patients with occlusal problems, we see many who have wandered from office to office, and no one could find out what the patient's problem was. Yet, after repositioning splint therapy, when we have the patient's mandibular position stabilized in centric relation and have eliminated the symptoms, we have unmasked the discrepancy and it becomes very apparent to anyone examining the occlusion now, why the problem existed (Fig. 13). We have literally stripped the veil off of the problem. We have eliminated the neuromuscular accommodation of the mandibular position to the existing occlusion, and placed the condyles in the proper centric relation position in the fossae. When this is done and the relationship captured accurately, we can now see how much the patient had to accommodate to get the teeth into intercuspation at the expense of the temporomandibular joints. Prior to the splint wear the musculature had postured and "splinted" the mandibular position, making the operator's manipulative efforts inadequate to disclose the true severity of the discrepancy. The fact that "true" centric cannot be located on most, if not all, patients

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on the first clinical attempt without resorting to the use of repositioning splint therapy, is a difficult concept to get across. Not because it is difficult to understand, but because dentists do not want to believe it. If you believe it, you have opened the door to more work and effort, and that is exactly what most people do not want. We think that the higher percentage of treatment success is well worth the extra work and effort. If a patient's mandibular musculature is tight or tense, or if there are TMJ noises, or facial pain, or occlusal wear, a repositioning splint is indicated, if you are going to render any kind of occlusal therapy (including orthodontic treatment). This should be done prior to any type of irreversible occlusal treatment. Some sizeable discrepancies are unearthed with the splint, although some treatment time, in terms of months, may be required to reach stability of the mandibular position. Again, we think it is impossible to formulate an appropriate treatment plan until a stable and comfortable centric relation of the mandible has been obtained. Indeed, it is impossible to know whether or not to put the patient through treatment until this is accomplished. We have seen too many cases that have failed miserably, in which equilibration, orthodontics, or restorative dentistry have been performed in an attempt to solve a TMJ problem. On many of these patients we have found, after splint therapy of several months, that the jaw relationship was so far out of the "ballpark" that orthognathic surgery and orthodontics would be required just to get close enough to begin "occlusal fine tuning". Yet this discrepancy could in no way be unveiled clinically by clever mandibular manipulation on the first few visits. As far as we are concerned, ANY CAPTURED OR MOUNTED CENTRIC RELATION RECORD OBTAINED WITHOUT FIRST ACHIEVING STABILITY ON A REPOSITIONING SPLINT IS OPEN TO QUESTION. We would make the above statement regardless of the centric registration technique employed, and regardless of the operator. We realize that this is a strong statement and an unpopular one at that. However, this has been demonstrated clinically time and again. Capturing and Stabilizing True Centric True centric relation of the mandible is a stable superior clinical limit position of the condyles against the articular discs, that can be captured clinically and reproduced time and again. Once a patient has been stabilized on the splint, any good centric registration technique will yield identical and verifiable centric positions of the mandible. Without first stabilizing the mandibular position, different types of centric registrations will yield different mandibular positions, as shown by J. Hart Long. True centric can be stabilized if there are no degenerative joint changes on a nongrowing patient. True gnathologic centric relation of the mandible, once attained, will appear to be within the normal range of positioning of the condyles in their fossae for most patients when cephalometric tomograms are inspected. There are some exceptions to this. However, as long as the patient is comfortable and the mandibular position is stable, the condyle-fossa relationship on the x-ray is not too significant. Patient comfort is what counts. We would not vary the mandibular position when comfort and stability have been attained, just to satisfy the normal x-ray definition of the

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condyle-fossa relationship. Centric Closure and Anterior Guidance Relief of symptoms alone is not the major purpose of the repositioning splint in our mode of therapy, as it is with many other approaches. The splint will relieve symptoms, but so will most anything that is placed between the teeth and disengages the occlusion. The objective in making the repositioning splint is to seat the condyles in the most superior position possible on every visit, and to adjust the occlusal surface of the splint to achieve maximum intercuspation at this position of the mandible at the most closed vertical dimension obtainable. The only variation to this would be in a case in which the vertical dimension had obviously been decreased due to loss of posterior teeth, and efforts to attain comfort at the closed vertical dimension had been unsuccessful. In addition to centric closure, an anterior guide ramp is created to act as anterior guidance to disclude the posterior teeth during movement out of centric. The anterior guidance must be the gentlest slope possible that will immediately disclude the posterior teeth. The ramp should have as many incisor contacts as possible in straight protrusion and in lateroprotrusion. The cuspids should be the main guiding inclines in lateral movements. The anterior teeth should have .0005" clearance from the ramp in centric closure, thus showing articulating paper marks, but having shimstock clearance. The repositioning splint is, therefore, a removable "mutually protected" occlusal scheme, that can be used to test the patient's response to a change in the occlusion without really doing something that is not reversible. The repositioner should be adjusted as soon as a change in mandibular position becomes evident. The adjustment is usually done by relining the occlusal surface of the splint with a self-curing acrylic resin. The mandibular postural changes during splint therapy are of three different types: 1. Changes due to relaxation of the musculature that postures the mandible incorrectly due to muscle contracture or spasms. 2. Changes due to elimination of intracapsular inflammatory fluid. 3. Changes due to remodeling or recontouring of the bony parts of the joints (e.g. condyles or fossae). Therefore, splint therapy must be continued until there has been no change in mandibular positioning in centric relation for at least three months. In some of the more difficult cases, where there is some radiological evidence of recontouring of bony parts of the joints, six months stabilization on the splint is a good indicator that it is all right to proceed with more definitive treatment.

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There is no reason to believe that, if comfort and/or stability cannot be achieved with the splint, it can be obtained by altering the occlusion permanently. Therefore, if symptoms cannot be relieved or stability attained with the splint, we will usually not proceed with treatment. This eliminates many failures before the fact. Splint therapy is indicated any time that there are symptoms present and when mandibular manipulation is difficult. It is wise to institute splint therapy prior to orthodontic treatment and stabilize the mandibular position for three months on any symptomatic case. This decreases the mobility of the ligaments of the TMJ's and allows the patient to learn where his mandible belongs, so that when orthodontic treatment is started the patient does not just subluxate and fit his teeth into centric occlusion again. It keeps the orthodontist from "getting lost" once again when treatment starts. After stabilization on the splint, a reasonable facsimile of centric can be obtained clinically on every visit until near the very end of treatment. Repositioning Splint Construction Because of the need for precision in the splint, some precautions must be taken in the fabrication of the models. First, the impression of the maxillary arch must be accurate. Teeth cannot perforate the impression material. If the impression is not accurate, take it over immediately. The alternative is to have to take it over later, after wasting laboratory and clinical time on a splint that doesn't fit into the mouth. Second, the impression must be poured immediately if alginate is used. This means taking the impression directly from the mouth to the laboratory and pouring the mounting stone into the impression without delay. After the mounting stone is in the impression, return to the patient to clean up, establish a date for insertion of the splint, and dismiss the patient. Third, the model must be made from an accurate stone. Mounting Stone made by the Whip-mix Corporation is ideal for this purpose. The setting expansion (0.08%) is the same as the stone used for dies and master casts. However, the strength of Mounting Stone is close to that of plaster. This enables the easy removal of the model from the splint without the danger of "springing" the acrylic, which ruins the splint as surely as would an inaccurate impression. The splint base is constructed from .080" Omnivac material or from Biocryl II material on the Biostar machine (Fig. 14). In using the Biostar, the material is formed under 4 atmospheres of pressure to insure a tight fit. The base of the splint should snap in tightly, with a minimum of material over the labial and buccal surfaces of the teeth. It is imperative that the splint base stay in place during closure, movement, and chewing. The Biocryl is stronger and more resilient and will last longer without fracturing. If, after stabilization, it is anticipated that the patient will remain on the splint for some time, it is suggested that an articulator mounting on a true hinge-axis be made and a heat-cured splint be made. If a centric relation record can be obtained at the exact vertical dimension of the splint and the vertical is not changed during the splint construction, then a mounting is not necessary.

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After the base of the splint is constructed, the material is tried in the mouth and the flanges adjusted to a minimal height that will give good retention. Only enough of the last molars should be covered to keep them from erupting, thus keeping the vertical dimension of the splint to a minimum. The material is cut forward on the palatal side, to keep the material off of the soft palate. The flanges of the base can best be finished with a knife blade to obtain the smoothest finish. The material is placed in the mouth and the mandible is manipulated into centric. The base material should be thinned posteriorly, where the first centric contacts are, to help construct the splint at the most closed vertical dimension. The trimming of the material should be done with a tapered Buffalo carbide acrylic bur in a slow-speed handpiece. After the base material has been prepared, the splint is now ready for the occlusal lining. The lining can be done in Trim, Fastray, Biocryl acrylic, or Stratford-Cookson Orthocryl. The clear Orthocryl or Biocryl are the most esthetic and the Orthocryl will probably hold up better than the Trim or Fastray for this purpose. A fairly thin mix of acrylic should be prepared and while the acrylic is being mixed, the occlusal surface of the splint material should be painted liberally with monomer. A cement spatula can be used to place the acrylic on the splint base. Having placed the splint in the mouth beforehand, one should note where the lower teeth fit the splint, so that he knows where to place the acrylic lining. The main thing at this stage is to take sufficient time to place the material equally on the posterior segments, and place sufficient material in the anterior part so that there is enough material for the anterior guide ramp from cuspid to cuspid. There is plenty of time, so don't rush through this part of the procedure. After spreading the occlusal lining over the splint base, paint it with monomer to get a smooth surface and a blending of the acrylic with the splint base. If any of the material leaks into the palatal area of the splint base, cover it with extra acrylic and paint with monomer, so that the palatal surface will not be rough to the tongue. It is impossible to polish the splint base material. Dry the acrylic a little with an air syringe and place the splint carefully into the mouth, making sure that the splint base is completely seated. With the chair leaned back, manipulate the patient's mandible in the following manner: Push down on the chin with the thumb of the right hand, while pushing up on the gonial angles with the forefinger and second finger. Keep the entire right arm stiff and apply distal pressure by leaning from the shoulder. This is most important. Pushing down on the chin makes the patient seat his own condyles, as he tries to close against the downward pressure at the chin. Hinge the patient slowly and lightly into the soft acrylic, and warn him that you do not want him to close and go through to the hard base underneath. You want him only to make light tooth prints into the soft material. Once he has done this, have him hold lightly and, using the cement spatula, even the edge at the incisal portion of the anterior guide ramp. Remove the splint from the mouth carefully, so as not to distort the acrylic, and allow it to set. If it is difficult to seat the condyles superiorly, it may be necessary to stand behind the patient, placing the forefingers of both hands on the chin, with the thumbs pushing the gonial angles upward

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and forward while the mandible is hinged closed with a lifting motion of both hands. The mandible is then being rotated from the superior-anterior seated position of the condyles, and no distal pressure need be applied. Downward pressure is applied to the chin in this manipulative technique also. After the material has set, a sharp pencil is used to outline the entire buccal and labial impressions of the lower cusps in the acrylic. The lathe, with a green acrylic fastcut wheel, can be used for the gross trimming of the occlusal lining and anterior ramp. The excess material is cut away, leaving the pencil mark at the very tips of the cusps. The remaining material is cut to a flat surface. After the bulk of the material has been trimmed, the remainder of the trimming is done with the carbide acrylic bur. The anterior guide ramp is cut at approximately 45 degrees from cuspid to cuspid, and the incisal edge of the guide ramp is made even in height all the way around. The acrylic is smoothed with the carbide bur in all areas and in the palate, so that everything is shaped flat in the posterior section and at 45 degrees on the anterior ramp. The height of contour of the posterior section should be at the pencil marks of the cusp tips. A course lab pumice is then used to smooth and polish the entire splint, as this cannot be done after equilibrating the occlusal stops. Care should be taken to leave the pencil marks at the cusp tips. After all the polishing has been completed, the marks of the anterior teeth can be erased with the pumice as the guide ramp is polished. The anterior markings should be just barely erased. Adjusting the Splint in the Mouth The splint is now brought back to the mouth and is equilibrated in centric using Accufilm, manipulating the mandible as described above. The equilibration is done by equalizing the posteriors until there is a dot for every posterior cusp and all dots are marking equally. As anterior marks show up, they are removed as the posteriors are equalized in contact. The posteriors should all hold shimstock, and the shimstock should slip through the anteriors when the posteriors are held tightly in occlusion. After equalized centric stops are obtained for the posteriors, the anterior guide ramp is adjusted and reduced in height, so that there is the gentlest possible lift of the posteriors immediately upon movement. The anteriors are adjusted to get the greatest number of anterior equalized contacts in protrusive and lateroprotusive movements, using a ribbon of a different color than that used to mark the posterior centric contacts. The lateral excursions should lift mainly on the cuspids. The ramp should be long enough to provide a glide, but should be short as possible in height. The anterior part of the ramp can be rounded over with the pumice wheel after the shaping is done, and then polished very carefully with fine pumice. The final testing of the splint should be done using a dark ribbon for the centric stops and a lighter colored ribbon for checking the excursion paths on the guide ramp, and to make sure that there are no balancing and working drags on the posteriors as the mandible is moved with pressure against the angle of the orbiting side to elicit side-shift. It is important that there be no posterior

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contact on lateral border movement and in protrusive. The cuspids should not be in contact with the guide ramp in protrusive. Ask the patient if everything feels equal when he bites. Take his word for what he feels at this point. If the condyles have been seated, the patient may feel some pressure in the joints as he bites. This is not uncommon. The patient is told that he may have some discomfort or even a headache the first day and that by the middle of the second morning, things should get pretty comfortable. By the second afternoon, the bite might feel slightly different and there may be some discomfort returning. As soon as this occurs, the patient should contact the office for an appointment, as the mandible has repositioned and the splint must be adjusted. The objective is to catch the patient before real pain sets in. Once pain has returned, it is difficult, if not impossible to manipulate the mandible properly. The adjustment schedule is usually as follows: 24-48 hours the first week. 48-72 hours the second week. 4-5 days the third and fourth weeks. 7-10 days the next several weeks. 3-4 weeks thereafter. If the patient is in extreme pain initially and it is not feasible to manipulate the mandible, a flat plane splint can be constructed in the same manner, but instead of building a guide ramp, just get equal contact of all teeth against the acrylic; grind the acrylic flat polish with pumice; and let the patient wear it full time for several days. Then have the patient in and reline the occlusal surface of the splint, as described above. Patients in severe pain or spasm can be given Valium with hot packs to the affected muscles, ultrasound treatments, and biofeedback therapy to aid in obtaining short-term relief and to allow mandibular manipulation, so that a satisfactory splint can be made. Drugs should not be employed later, because it is important to know whether the patient is responding favorably to the occlusal change provided by the splint. Drugs only serve to confuse the issue. For the splint to be effective, it must be worn ALL THE TIME EXCEPT FOR CLEANING. If this is not done, the splint is only providing symptomatic relief, and you will never achieve a stable mandibular position. Patients should be instructed not to touch teeth together when the splint is out of the mouth for cleaning. The patient must wear the splint while eating. There are no exceptions. The splint can be equilibrated only if there is no positional change of the mandible (e.g. to equalize stops). If there is any repositioning, the splint should be relined. In the event that there is a disc displacement that has been diagnosed from arthrograms of the temporomandibular joints, it may be necessary to construct the initial splint in a forward and slightly subluxated position, and allow the patient to wear the splint in this manner for several weeks to a

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month. This will serve to place the condyles under the articular discs in many instances. After the initial several weeks and if the clicking has disappeared, or it can be established that the condyles have been placed in contact with the articular discs, the mandible can slowly be worked towards centric by adjusting the splint a little at a time, as described before. The repositioning splint has proven to be a valuable differential diagnostic tool, as well as giving patients relief from pain. If the splint is used as described above, you are bound to effect a higher percentage of successful treatment on those cases that you decide are good candidates for occlusal therapy. Obviously, if some favorable response is not obtained with splint therapy within a reasonable period of time, it may be that there are some other etiological factors at work. It would be best to refer the patient to the appropriate therapists, if the problem does not seem to be occlusion related. Temporomandibular paindysfunction is a multifaceted problem and we should be aware that occlusal therapy is not the only treatment modality. FABRICATION OF A REPOSITIONING SPLINT

1 Accurate stone model. Plaster is not adequate.

2 Base trimmed to approximately 5mm at the thinnest point.

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3 With model in vacuum former, a 0.080" clear resin sheet is heated until it sags approximately ¾".

4 While vacuum is still on, tightly adapt the resin to the interproximals and occlusal anatomy of the teeth.

5 With an acetate marking pen, mark the separation line.

6 Acrylic trim bur.

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7 With the acrylic trim bur, follow the separation line cutting through the resin shell.

8 Cut under the teeth with the bur. This allows the teeth to be fractured from the rest of the model, so that the resin shell can be separated from the model without fracturing or distorting the shell.

9 Pry with a lab knife to fracture the model and separate the teeth from the model base.

10 A carbide bur for the straight handpiece is used to trim the resin and finish the acrylic used in the fabrication of the splint.

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11 Trim and smooth the margins.

12 No. 2 and/or a No. 4 round bur is used in the straight handpiece to remove internal interferences. An indicator paste such as P.l.P. may be helpful. Once the resin shell has been fitted to the teeth, the mandible is manipulated to reveal the initial prematurity in CR (see Steps 18 & 19). The resin shell is reduced until the thinnest area is about 1mm in thickness. Greater thickness will require excessive opening in the anterior. Less thickness will result in weakness and subsequent fracture of the splint. When the posterior interferences have been reduced, acrylic such as Trim, Snap, or Fastray, is mixed in a dappen dish.

13 Mix acrylic in a dappen dish.

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14 Prepare the surface of the resin shell by moistening it with monomer. Add acrylic to occlusal surfaces.

15 Fill lingual interproximals with acrylic for strength and for esthetics.

16 Moisten an index finger with saliva from the patient's mouth.

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17 With the moistened index finger, smooth the acrylic on the lingual and occlusal.

18 For greatest accuracy and control, manipulate the mandible with both hands from behind the patient's head.

19 The thumbs press downward and back, while the fingers support the angle of the mandible, seating the condyles upwards and slightly backwards into the fossae. Maintaining this pressure, gently close the mandible by rotating the condyles on their hinge axis.

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20 Manipulating the mandible with one hand is possible, but more likely to produce errors in closure. If attempted, an anterior stop should be provided with a finger.

21 As the mandible is closed, the anterior stop can be maintained with thumb and finger.

22 The mandible is gently guided into the CR position and closed into the acrylic.

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23 Regardless of the technique, the mandible should be seated primarily upward as well as backward into the most reproducible position.

24 While the acrylic is setting, the mandible is tapped into CR and then opened slightly several times. This avoids locking the teeth and accommodates any minor distortion that may otherwise occur during the setting of the acrylic.

25 After the acrylic is set, mark the depressions made by the mandibular cuspids. Use a standard graphite writing pencil.

26 Mark the path of the cuspid excursion on the acrylic. With the pencil tip, mark all indentations made by any cusp tips.

27 With a carbide bur, remove all excess acrylic around the indentations

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in cuspid-to-cuspid area.

28 Grind out all contact in the posterior. Allow about 2mm between teeth and the splint.

29 With only anterior support, the condyles tend to seat upward and backward.

30 Occlusal marking shows posterior clearance. In cases where there is evidence of either posterior capsulitis or a large closing click, the procedure illustrated in Steps 28, 29, & 30 may be exactly the wrong thing to do! Leaving these particular patients with only anterior support may increase the damage to the posterior area of the capsule and result in both pain and more damage than good.

31 Head of condyle is near posterior border of the disk. Further movement upward and/or backward will drive the disk foreward and leave the condyle seated on soft tissues rather than the articular disk.

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32 As the mandible is manipulated, there is a "CLICK" and a perceptible movement as the condyle slips off the disk.

33 With the disk displaced anteriorly, the condyle pinches on the tissues posterior to the disk. Note: this is a reproducible position which . is rearmost and uppermost. It is pathogenic and often painful. Steps 34 & 35 illustrate one adaptation to the case with either a late click or posterior capsulitis. The inset shows that small "stops" have been left at the distal aspect of the CR contacts for each cusp tip of the holding cusps on the mandible. The mandible is manipulated slightly anterior to the point of the click, while the acrylic is setting. Except for the mandibular manipulation and the "stops", the splint therapy is the same as for routine patients.

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35 After approximately 3 days on the splint with only anterior support, the patient is reappointed and the posterior is relined with plastic to provide support in CR. The same basic procedure is used to reline the posterior as was illustrated in Steps 13-27, except that a mutually protected occlusion is established.

36 Condyles seated in CR with the cusp tips of all mandibular posterior teeth in simultaneous contact.

37 Occlusal markings on a properly adjusted splint. Posterior cusp tips contact simultaneously in CR. The four incisors engage in protrusive excursion. The cuspids engage in lateral border movements.

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38 Mid-sagittal section showing CR contacts.

39 The incisors clear in CR by 0.0005". All anterior teeth clear the splint in gentle CR closure. This includes the cuspids as well as all four incisors. These teeth engage immediately upon any eccentric excursion.

40 Protrusive guidance from the anterior ramp of the splint and from the condyles against the articular surface of the glenoid fossa.

41 Mid-sagittal section of mandible against a splint in protrusive excursion. Note: only the incisors contact the splint.

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42 Incisors are engaged immediately upon protrusive excursion. Note the slight lingual concavity on the splint. Upon clenching, the incisors and cuspids will contact the anterior ramp in CR. Instantly, on beginning lateral excursions, the cuspids contact and disclude all posterior teeth. The four incisors instantly disclude the rest of the teeth in protrusive.

43 The simple dots on the occlusal table represent CR contacts.

44 Occlusal view of properly adjusted splint. Broken line indicates plane of section in 45 & 46.

45 Section in a frontal plane. Right side illustrates the cusps seated in the acrylic which has been added to the resin shell. Left side illustrates adequate reduction of the acrylic.

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46 Each cusp has its own unique path in each excursion. Relative distances from the cuspids and the condyles determine the relative influence that these determinants of occlusion have on the path of each cusp during border movements.

47 Excursions are checked with mylar marking film (0.0008" thin). Paper and silk marking materials will not detect interferences accurately enough to allow the freedom from trauma that is needed in some sensitive cases. This figure illustrates the identification of a small working interference.

48 A rim of resin is left over the incisal edges of the anterior teeth until the posterior reline is completed. This aids in avoiding getting small amounts of the acrylic onto the internal of the splint and thus displacing the splint.

49 Once the mutually protected occlusion has been

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

established, the rim is removed from the labial of the anterior teeth.

50 Completed splint.

51 In CR, 0.0005" shim will not catch between the incisors and the anterior ramp.

52 Anterior view of right lateral excursion on properly adjusted splint.

53 Anterior view of left lateral excursion on properly adjusted splint.

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

54 In CR, the 0.0005'' shim holds between the buccal cusp tips of all mandibular molars and bicuspids. The patient cannot detect any points which have greater pressure than any others in CR.

55 Centric relation, lateral excursion and protrusive excursion marks on a properly adjusted splint in an ideal mouth. ARMAMENTARIUM FOR FABRICATION OF OCCLUSAL SPLINT • Vacuum adapter e.g. Omnivac, Biostar, etc. • Clear resin 0.08" thick for adapting over the model. • Acetate marking pen: e.g. any waterproof felt tip. • Acrylic trim bur. • Flame-shaped H.P. bur for shaping acrylic. • Dappen dish or silicone rubber substitute. • Small metal spatula for mixing acrylic in dappen dish. • Dropper bottle (½oz.) for acrylic monomer (e.g. Trim, Snap, etc.). • Squeeze-type dispenser (3oz.) . for acrylic polymer powder. • Articulating paper forceps: minimum of 3 pair per setup.

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

• Mylar marking film, two colors. (Red & Green = best combination) This material is 0.0008" thick. Thicker material will not allow the clinician to achieve the level of accuracy which is necessary is some cases. Sources: Parkell, Almore, et.al. • Shim stock for checking contacts (0.0005"). Source: The Artus Corp., P.O. Box 511, Englewood, New Jersey 07631. READING SPLINT MARKINGS The marks in Figure A were obtained from mandibular excursions from CR on green Accufilm by performing right and left lateral and protrusive excursions. Then, CR was marked with black Accufilm. The mandible is in an Angle Class I relationship with no asymmetry and 28 teeth in good alignment. The occlusal aspect of the splint has no irregularities. Figure B illustrates the working path (W), non-working path (NW), and the protrusive path (P) described by a mandibular cusp as it moves in border movements against the occlusal surface of the splint.

Figure C illustrates ideal post-adjustment markings on a repositioning splint. THE ESTHETIC PROBLEM OF SPLINTS IN OPEN BITE CASES

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

1 In Angle Class II cases, the mandible is often postured into a Class I position at the expense of the TMJ . This figure illustrates a centric occlusion (CO) which requires the condyles to be subluxed.

2 The same case as in 1 but with the condyle seated in CR. Posterior interferences separate the anterior teeth.

3 Anterior view of condition illustrated in 2. This represents an esthetic problem, if a splint is required.

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

4 When the necessary thickness of acrylic and splint base is inserted between the posterior teeth, the anterior teeth are separated even more.

5 Anterior view of a splint in the case illustrated in 4.

6 Right lateral border movement requires an anterior ramp long enough to disclude the posterior teeth. No compromise is acceptable here.

7 Left lateral border movement requires adequate ramp for

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

clearance of the posterior teeth.

8 Protrusive excursion on a properly prepared splint for an anterior open bite case. Note that the posterior teeth on the left side just clear the occlusal surface of the splint.

9 Properly prepared splint on an open bite case may have a wide band of acrylic showing in the front. (TO BE CONTINUED)

RONALD H. ROTH

DONALD A. ROLFS

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume Feb

FIGURES Fig. 13

Fig. 13 A,B,C. Standard orthodontic models of a symptomatic TMJ patient prior to repositioning splint therapy. D,E,F. Models mounted on a Stuart articulator at the conclusion of splint therapy, revealing a huge discrepancy between centric relation and centric occlusion. (Photos courtesy of Dr. Robert E. Williams, Mountain View, California.)

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JCO on CD-ROM (Copyright © 1998 JCO, Inc.), Volume 1981 Feb(100 - 123): Functional Occlusion for the Orthodontist - Part 2

Fig. 14

Fig. 14 A. Repositioning splint constructed with an Omnivac .080" base and Fastray occlusal lining. B. Repositioning splint in a protrusive excursion. C. Occlusal view of centric stops on a heat-processed acrylic repositioning splint. D. Occlusal view of centric stops on a repositioning splint constructed with a Biocryl II base and Orthocryl occlusal lining.

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