Long-term clinical outcomes of posterior monolithic and porcelain-fused zirconia crowns: A retrospective cohort study.

STATEMENT OF PROBLEM: Monolithic zirconia crowns and porcelain-fused zirconia crowns have been evaluated with in vitro studies, but clinical evidence of their longevity is limited. PURPOSE: The purpose of this retrospective cohort study was to compare the long-term cumulative survival and success rates of posterior monolithic and porcelain-fused zirconia crowns and to investigate risk factors associated with complications. MATERIAL AND METHODS: The study included 235 patients and 255 crowns (dropout rate:10.9%). Clinical data were analyzed for single posterior monolithic zirconia crowns and porcelain-fused zirconia crowns placed consecutively during a 10-year period and for subsequent events during follow-up. Survival curves for the monolithic zirconia crown and porcelain-fused zirconia crown groups were drawn using Kaplan-Meier analysis. Statistical differences between groups were tested using the log-rank test (alpha=.05). The Cox proportional hazards analysis was used to identify risk factors for crown and abutment tooth complications. RESULTS: The 10-year cumulative survival rates of the monolithic zirconia crown and porcelain-fused zirconia crown groups were 86.0% (95% CI, 72.8 to 99.1%) and 71.0% (95% CI, 54.6 to 87.9%), respectively. The monolithic zirconia crown group had a higher survival rate than the porcelain-fused zirconia crown group, but the difference was not statistically significant (P=.108). The 10-year cumulative success rate was higher in the monolithic zirconia crown group than in the porcelain-fused zirconia crown group, but the difference was not statistically significant (P=.071). Two risk factors were identified for crown complications alone: a molar rather than premolar crown (P=.014, hazard ratio [HR]=6.012) and a maxillary rather than a mandibular crown (P=.003, HR=9.487). CONCLUSIONS: The 2 different types of crowns exhibited application site dependency for crown complications but not for abutment tooth complications.