Survival and complications of implant-supported cantilever fixed dental prostheses with zirconia and metal frameworks: A retrospective cohort study

Abstract

Background: Current evidence about long-term survival of all-ceramic implant-supported cantilever fixed dental prostheses (cFDP) is limited. Purpose: To evaluate the survival and complication rates of all-ceramic and metal–ceramic implant-supported cFDPs located in anterior and posterior sites, under consideration of risk factors. Methods of study: The retrospective analysis compared an experimental group (75 implant-supported cFDPs among 48 patients [mean age 60.47 ± 9.25 years; 21 men]; mean observation period 3.56 years) with a control group (300 implant-supported non-cantilever FDPs [ncFDP] among 241 patients [mean age 62.85 ± 10.72 years; 109 men]; mean observation period 7.25 years). Kaplan–Meier estimates were used to describe the long-term survival and success of both groups. Log-rank tests were used for group comparisons. Mixed-effects Cox proportional hazards regression models were used to examine the effects of restoration- and site-specific risk factors. A random intercept was included in the models to take multiple FDPs per patient into account. Results: Five-year cumulative survival until loss of restoration was 97.1% (95% confidence interval [CI] 0.93–1.00) for cFDPs and 97.0% (95% CI 0.95–0.99) for ncFDPs. Ten-year survival was 93.7% (95% CI 0.86–1.00) for cFDPs and 92.8% (95% CI 0.87–0.98) for ncFDPs, no difference between the survival curves of these groups was observed. Success differed between cFDPs and ncFDPs (pLog = 0.002), zirconia and metal frameworks (pLog < 0.001), and provisional and definitive cements (pLog = 0.025). The effects of the variables “framework material” and “attachment method” were confirmed in a mixed-effects Cox regression model. Loss of retention was the predominant complication for both cFDPs and ncFDPs and usually affected provisionally cemented FDPs. Conclusions: cFDPs do not differ from ncFDPs with regard to long-term failure, whereas additional complications were higher for cFDPs. Fewer complications were observed for zirconia frameworks without occlusal veneers and definitive cemented FDPs. Clinical trial registration: the trial has no registration number because it commenced before January 31, 2017.