Purpose: This retrospective study investigated the frequency and time history of chipping and facing failures, recurrent caries (RC), periodontitis (PE), and loss of retention (LR) of porcelain-fused-to-metal (PFM) single crowns.
Materials and methods: A total of 997 PFM single crowns had been inserted according to a standardized treatment protocol from January 1984 to May 2009. The frequency and time history of chipping and facing failures were evaluated, as were possible risk factors from historical clinical data. Risk factors were bruxism, the type of antagonist, and the location of crowns (mandible, maxilla, anterior, posterior). The survival times of crowns were estimated using Kaplan-Meier (KM) analysis.
Results: The median follow-up time calculated with the inverse KM method was 4.33 years. Anterior and posterior PFM crowns showed 5-year survival rates (time to crown replacement) of 96.4% and 97.5% and 10-year survival rates of 92.3% and 95.9%, respectively. Chipping was found in 17 (1.7%) of the 997 PFM crowns. According to the KM method, the 5- and 10-year free-of-event-rates for chipping of anterior crowns were both 98.9%, and the rates for posterior crowns were 98.2% for 5 years and 97.3% for 10 years. Thirteen patients showed RC (1.3%) and 144 (14.4%) PE. The 5-year free-of-event-rate for RC was 98.7% and the 10-year free-of-event rate was 97.2%. For PE, the 5-year free-of-event-rate was 85.8% and the 10-year free-of-event rate was 72.2%. The 5- and 10-year free of- event-rates for LR were 92.2% each for anterior teeth and 97.1% each for posterior teeth.
Conclusions: Patients with PFM crowns may expect long-term survival for their restoration. Clinical complications are rare. Chipping of the veneer or loss of retention may occur during the first few years. While chipping of the veneer may occur during the first few years, the frequency of caries or periodontitis increases with the length of oral service and with age.