Outcomes of abutment teeth with double crowns over an observation period of 27 years.

PURPOSE: The aim of this retrospective study was to determine the outcome of double crowns (DCs) using pooled data over a period of 27 years. METHODS: Billing data were obtained from the digital accounting system of a university dental clinic. All DCs inserted and invoiced from January 1, 1992, to December 31, 2019, were collected. The maximum observation period of a DC was determined by a recorded follow-up or the occurrence of a target event. Target events were divided into primary, i.e., tooth extraction, and secondary, i.e., failure of DC, types. The dataset was analyzed using descriptive statistics and Kaplan-Meier survival and multivariate Cox regression analyses. RESULTS: A total of 4,097 tooth-supported DCs in 1,148 patients were included in the analysis. The mean observation period for individual DC was 5.32 years. The cumulative survival rates at 5 and 10 years for the primary target event were 89.7% and 73.8%, respectively. The cumulative survival rates at 5 and 10 years for the secondary target event were 83.6% and 60.6%, respectively. In the multivariate analysis, age and metal denture bases were significantly associated with both target events. CONCLUSIONS: This study confirmed DCs as a reliable and long-term successful treatment option for anchoring removable partial dentures. The use of a metal denture base and a younger patient age might reduce the risk of complications.