Risk of Secondary-Caries/Endodontic Treatment of Porcelain-Fused-to-Metal Fixed Partial Dentures

Introduction: This retrospective study investigated the frequency and time history of secondary caries (SC) or need of endodontic treatment (EDT) 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 the FPDs, SC and the need of EDT were evaluated from the clinical history data. Continuous variables were presented as means and standard deviations. 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 38 months. The five years survival rate of all PFM-FPDs was 94%, and 87% for 10-years. SC had 19 (2.9%) and EDT 33 (5.0%) events of the PFM-FPDs. According to KM, the five years free-of-event-rate for SC was 98%, and 95.2% for 10years, respectively. The five years free-of-event-rate for EDT was 92.4%, and 90.4% for 10 years, respectively. The annual hazard rate of SC of PFM in the first year was 0.004, i.e. 4 of 1000 person years of exposure had SC and remained almost constant for the next 11 years. From year 13 on, the hazard rates increased in an exponential way from 0.06 to 0.36 (year 19). The annual hazard rate of EDT in the first year was 0.02 staying nearly constant until year 8 with an annual hazard rate of 0.009. After 8-years no more EDT events occurred. Conclusions: Patients with PFM-FPD can expect a long survival rate of their restoration. The risk of EDT remained constant within the first 8 years and dropped to zero for the following years, while the risk of SC is very low in the first years and increased exponentially after 12-years.