Chipping/facing failures of Porcelain-Fused-to-Metal Fixed Partial Dentures

Introduction: This retrospective study investigated the frequency and time history of chipping / facing failures of porcelain-fused-to-metal (PFM) three- and four unit fixed partial dentures (FPDs). Material and method: 654 PFM FPDs were inserted according to a standardized treatment protocol between Jan. 1984 and May 2009 at the Department of Prosthodontics. The frequency and time history of chipping or facing as well as possible risk factors were evaluated from the clinical history data. Risk factors were bruxism, type of antagonists (fixed versus removable dentures) or location of the FPDs (mandible, maxilla, anterior, posterior area). Continuous variables were presented as means and standard deviations (SD). Categorical variables were presented as absolute numbers and proportions. The survival times of FPDs were estimated by means of Kaplan-Meier analysis (KM). Results: The median follow-up time calculated with the inverse KM method was 3 years. The five years survival rate (time to renewal of a FPDs) of all PFM FPDs was 94%, and 87% for ten years. Chipping had 28 (4.3%) of the PFM FPDs. According to KM, the five years free-of-event-rate for chipping was 95%, and 94% for 10 years. Possible risk factors such as bruxism, type of antagonists, maxilla, mandible, posterior/anterior area had no statistically significant influence on chipping / facing failures. The annual hazard rate of chipping of PFM in the first year was 0.03, i.e. 3 of 100 person years of exposure had chipping. For the next 6 years, the annual hazard rates dropped to 0.009, 0.003, 0.007, 0.004, 0.005 and 0.007, so about 3 to 9 of 1000 person years of exposure had chipping. Conclusions: Patients with PFM FPD can expect a long survival rate of their restoration. During the first year, the risk of chipping may be higher than within the following years.