Purpose: The purpose of this study was to evaluate survival rate and the reasons of failure of fixed dental prostheses (FDPs) without having regular maintenance in a long-term after insertion. Materials and methods: The subjects were 55 patients (69 FDPs, 142 abutment teeth) who had received no regular maintenance after insertion of FDPs at the Prosthodontic Clinic, Tohoku University Dental Hospital in Japan from 1983 to 1989. Extraction of abutment teeth or removal of FDPs was considered as failure. Abutment teeth and FDPs requiring additional treatments were considered as the complications. The survival curves were analyzed using the Kaplan-Meier method. The reasons for failures and their frequency as well as complications were also examined. Results: The average follow-up period was 16.5 years. 14 out of 142 abutment teeth were extracted, resulting in 10% failure rate. 22 out of total 66 FDPs were removed; the failure rate of FDPs was 33%. The most common reason for the failure and complication was periodontal disease. The mean value of plaque index was 43.2%. The analysis of the survival curves with the Kaplan-Meier method showed that the survival rates of FDPs at 15 years after insertion were 74%. As the status before treatment was not clearly stated, we cannot make an easy comparison; however, our data presented very similar results with reports from previous long-term clinical studies. Conclusion: This study suggested that the abutment teeth and FDPs in patients without regular maintenance had many periodontal problems due to dental plaque.
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