18-year longitudinal study of cantilevered fixed restorations.

One hundred thirty-seven cantilevered fixed partial dentures made between 1974 and 1990 were clinically and radiographically evaluated. Thirty-three of the prostheses were located in the mandible (11 in the anterior and 22 in the posterior region) and 104 were located in the maxillae (58 anterior prostheses and 46 posterior prostheses). Median duration was 84 +/- 3.6 months. During the 18 years, 41 (30%) failed. Of those that "failed," 28 (68%) were in the maxillae and 13 (32%) were in the mandible. Reasons for failure included abutment fracture (4), loosening with or without caries (18), secondary caries (9), fracture of prosthesis (2), fracture of extension (1), periodontal problems (6), and apical reaction (1). Failures occurred significantly more when endodontically treated abutments were used. More mandibular restorations failed than did maxillary units, but the difference was not significant. The prosthesis length ratio and the crown length-bone ratio did not influence the failure rate. The overall success rate of cantilever fixed prostheses was 70% over a period of 18 years.