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.