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Fracture of a fixed partial denture abutment: A clinical report Ronald G. Verrett, DDS, MS,a and David A. Kaiser, DDS, MSDb Department of Prosthodontics, University of Texas Health Science Center at San Antonio Dental School, San Antonio, Texas Commonly observed complications associated with a conventional fixed partial denture (FPD) include loss of retention and tooth fracture. This report describes the occurrence of an unusual FPD abutment fracture and subsequent treatment. The distal abutment of an FPD developed severe periodontal disease with mobility. The anterior abutment fractured in the middle of the clinical crown and experienced cement failure. (J Prosthet Dent 2005;93:21-3.)

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ixed partial dentures (FPDs) have been shown to exhibit clinical complications due to a wide variety of factors. In a review of the literature, Goodacre et al1 identified the most common FPD complications as caries, need for endodontic treatment, loss of retention, esthetics, periodontal disease, tooth fracture, and prosthesis fracture. In that review, fracture of an abutment tooth occurred in 3% of prostheses. The technical and biomechanical complications for FPDs may result in loss of retention, abutment tooth fracture, and prosthesis fracture. Technical failures occur more frequently in FPDs with at least 1 cantilever extension pontic, with the rate of failure increasing as the length of the cantilever span increases.2,3 Fracture of an FPD abutment adjacent to a cantilever has been reported to occur twice as frequently as fracture of an abutment not adjacent to a cantilever.4 Abutment fractures in conventional FPDs have also been documented in longitudinal clinical studies5; however, abutment fracture of the type reported here is infrequent.6,7 This clinical report describes an unusual fracture of an FPD abutment that occurred within the retainer of a conventional FPD and the subsequent treatment.

CLINICAL REPORT A 69-year-old woman reported to the University of Texas Health Science Center at San Antonio Dental School clinic with a chief complaint that the ‘‘bridge on the upper right side was loose.’’ The patient reported that the FPD had been inserted 12 years ago (Fig. 1). The FPD was found to be loose at the anterior abutment (maxillary right second premolar) but remained cemented on the distal abutment (maxillary right second molar). Clinical and radiographic examination revealed that the distal abutment had periodontal probing depths of 8 to 9 mm and exhibited Class III mobility (Fig. 2). The FPD was successfully removed and the maxillary right second premolar abutment was found to be fractured in the middle of the clinical crown, between the a

Assistant Professor. Professor.

b

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Fig. 1. Maxillary right posterior FPD at time of insertion (12 years previous).

occlusal surface and the finish line of the preparation (Fig. 3). This abutment had remained asymptomatic despite the fracture of the coronal tooth structure. The margin remained intact around the circumference of the preparation. The patient was informed of the clinical findings and was advised that the maxillary right second molar was not restorable due to severe periodontal pathology. The maxillary right second premolar had a widened periodontal ligament space (Fig. 3), which is often indicative of occlusal trauma. This finding was related to the tipping forces transmitted to this abutment during occlusal loading of the mobile distal abutment of the FPD. It was noted that the mandibular right first molar contacted the distal marginal ridge area of the retainer on the maxillary right second premolar. The possibility of supraeruption of an unopposed mandibular second molar and diminished masticatory ability on the right side of the arch following extraction of the maxillary second molar was discussed. Treatment options were presented that included replacement of the maxillary right molars with a removable partial denture (RPD) or with implant-supported crowns that would likely require adjunctive osseous augmentation. The patient declined the implant option owing to financial considerations as well as the RPD option because she did not want to wear a removable prosthesis. The patient stated that her desire THE JOURNAL OF PROSTHETIC DENTISTRY 21

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Fig. 2. FPD at time of patient presentation with distal abutment exhibiting 8 to 9 mm periodontal probing depths and Class III mobility.

VERRETT AND KAISER

Fig. 3. Removal of FPD revealed horizontal fracture through anterior abutment.

Fig. 4. Maxillary right second premolar received endodontic treatment and prefabricated dowel with core foundation. FPD was sectioned and premolar crown was recemented.

was to retain the maxillary second premolar and to have the second molar extracted. Endodontic treatment of the maxillary right second premolar was accomplished to place a dowel-retained foundation restoration. The most common dowel and core complication has been reported to be loosening of the dowel and root fractures.8 Root fractures have been reported to account for 3% to 10% of dowel and core complications, and cemented dowels have been found to cause the least intraradicular stress.8 A prefabricated passive parallel dowel (ParaPost Plus; Coltene/ Whaledent, Cuyahoga Falls, Ohio) was adapted to the canal space and cemented with glass ionomer cement (Ketac-Cem; 3M ESPE, St. Paul, Minn). A prefabricated post was selected because it was less expensive and did not require the additional appointment needed to restore the second premolar with a custom-cast dowel. According to Summitt et al,9 prefabricated dowels have been shown to exhibit greater fracture resistance than custom-cast dowels in laboratory studies and to provide a more favorable prognosis in retrospective clinical studies. 22

Fig. 5. Increased mobility of distal abutment (A), combined with occlusal forces (B), created shear forces between abutment anterior abutment and axial walls of retainer. These forces may result in fracture of abutment (C).

The FPD was then sectioned at the interproximal embrasure between the maxillary second premolar and the first molar, and the resultant second premolar crown was repolished. The crown was placed on the tooth and marginal integrity was clinically confirmed. A core foundation of the coronal portion of the maxillary right second premolar was accomplished using an autopolymerizing hybrid, filled resin composite, reinforced with titanium (Ti-Core; Essential Dental Systems, Hackensack, NJ). The resin composite was placed on the tooth and the crown was fully seated, shaping the core foundation and simultaneously cementing the crown (Fig. 4). The nonrestorable maxillary second molar was extracted. VOLUME 93 NUMBER 1

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DISCUSSION This clinical report describes the catastrophic failure of an FPD. The etiology was severe periodontal disease localized to the maxillary second molar that permitted excessive forces on the second premolar abutment. A biomechanical challenge was created when the excessively mobile distal abutment was rigidly connected to an abutment with only limited physiologic mobility. When an excessively mobile FPD abutment is subjected to an occlusal force, a torquing force is created on the other abutment that may result in cement failure or fracture of the abutment (Fig. 5). The forces transmitted to the anterior abutment in this instance are similar to the forces that occur on a cantilever FPD abutment adjacent to the cantilever section when the cantilever is subjected to occlusal loading.

SUMMARY An FPD abutment may fracture or the cement within a retainer can fail when subjected to excessive forces. Fortunately, retrospective clinical studies of conventional FPD complications have concluded that abutment fracture of the type reported is infrequent. REFERENCES 1. Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JY. Clinical complications in fixed prosthodontics. J Prosthet Dent 2003;90:31-41.

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2. Karlsson S. Failures and length of service in fixed prosthodontics after long-term function. A longitudinal clinical study. Swed Dent J 1989;13: 185-92. 3. Randow K, Glantz PO, Zo¨ger B. Technical failures and some related clinical complications in extensive fixed prosthodontics. An epidemiological study of long-term clinical quality. Acta Odontol Scand 1986;44: 241-55. 4. Ha¨mmerle CH, Ungerer MC, Fantoni PC, Bra¨gger U, Bu¨rgin W, Lang NP. Long-term analysis of biologic and technical aspects of fixed partial dentures with cantilevers. Int J Prosthodont 2000;13:409-15. 5. Valderhaug J. A 15-year clinical evaluation of fixed prosthodontics. Acta Odontol Scand 1991;49:35-40. 6. Laurell L, Lundgren D, Falk H, Hugoson A. Long-term prognosis of extensive polyunit cantilevered fixed partial dentures. J Prosthet Dent 1991;66: 545-52. 7. Cheung GSP, Dimmer A, Mellor R, Gale M. A clinical evaluation of conventional bridgework. J Oral Rehab 1990;17:131-6. 8. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: a literature review. Part 1. Success and failure data, treatment concepts. J Prosthodont 1994;3:243-50. 9. Summitt JB, Robbins JW, Schwartz RS. Fundamentals of operative dentistry. 2nd ed. Carol Stream (IL): Quintessence; 2001. p. 551. Reprint requests to: DR RONALD G. VERRETT DEPARTMENT OF PROSTHODONTICS UTHSCSA DENTAL SCHOOL 7703 FLOYD CURL DRIVE, MSC 7912 SAN ANTONIO, TX 78229-3900 FAX: 210-567-6376 E-MAIL: [email protected] 0022-3913/$30.00 Copyright Ó 2005 by The Editorial Council of The Journal of Prosthetic Dentistry.

doi:10.1016/j.prosdent.2004.10.009

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