An Up to 20-Year Retrospective Study of 4-Unit Fixed Dental Prostheses for the Replacement of 2 Missing Adjacent Teeth

Purpose: This study evaluated treatment outcomes of 4-unit porcelain-fused-to-gold fixed dental prostheses (FDPs) replacing 2 adjacent missing teeth. Materials and Methods: A total of 102 FDPs made in an undergraduate university clinic for 73 patients were evaluated for up to 20 years, with a mean survival follow-up time of 11.4 years. All patients were offered an oral health maintenance program. Treatment failures were divided into irreversible (loss of FDPs/finish line involved) or reversible (FDPs and finish line intact after conservative treatment) complications and into biologic and technical/patient-related failures. Results: The Kaplan-Meier overall estimated survival rate was 68.3% at year 20. There was a statistically significant difference (P = .007) between the survival rates in the maxilla for the vital group (73.8%) and those for the root canal-treated group (25.1%). Comparing the survival rate in the root canal-treated group for the restorations in the maxilla (25.1%) versus the mandible (66.8%), a statistically significant difference (P = .011) was found. The main reason for irreversible failure was caries (32.0%). Conclusion: The estimated successful outcome of 4-unit FDPs over an up to 20-year period is considered favorable and should be compared with the survival rates of other treatment options for the replacement of 2 adjacent teeth. Occurrence of a previously reversible complication appears to be a predictive factor for an irreversible complication later on. A reversible complication within the first 2 years will lead to an early irreversible complication.