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Purpose: The aim of this retrospective cohort study was to evaluate the clinical performance of zirconia-based implant-supported single crowns and fixed dental prostheses (FDPs) made by 15 members of the Italian Academy of Prosthetic Dentistry (AIOP) over a time period of up to 5 years. Materials and Methods: One hundred thirtyone patients were treated with a total of 210 zirconia-based single crowns and FDPs on implants in anterior and posterior regions. A cohort group with parafunctional habits was compared with patients without parafunctional habits according to the esthetic, functional, and biologic United States Public Health Service criteria modified by the FDI World Dental Federation. Results: The estimated cumulative survival (ECS) and standard error (SE) of all restorations on implants was 91.95% ± 1.39%, and the estimated cumulative success (ECSs) and SE was 88.37% ± 1.72%. The ECS of single crowns and FDPs was 91.25% ± 3.69% and 95.23% ± 2.28%, respectively, and the estimated cumulative success rates were 88.84% ± 2.05% and 87.96% ± 3.16%, respectively. Mechanical failures, including four zirconia core fractures, three hairline cracks, four chippings, and five delaminations of the ceramic veneering material, were recorded during a 1- to 5-year observation period. The odds ratio of 3.39 (95% confidence interval: 1.18 to 9.73) showed a moderate association between parafunction and failure. Conclusions: Zirconiabased implant-supported restorations showed encouraging clinical results over a period of up to 5 years, but more clinical data are needed before these restorations can be considered a viable treatment alternative. Mechanical failures were primarily observed in patients with parafunctions.

The aim of this retrospective cohort study was to evaluate the clinical performance of tooth-supported zirconia-based fixed dental prostheses (FDPs) made by 15 members of the Italian Academy of Prosthetic Dentistry over a time period of up to 5 years.Ninety-eight patients were treated with a total of 137 zirconia-based FDPs in anterior and posterior regions using primarily chamfer or knife-edge tooth preparations. The cohort group with parafunctional habits was compared with patients without parafunctional habits according to the esthetic, functional, and biologic United States Public Health Service criteria modified by the FDI World Dental Federation.The estimated cumulative survival of all restorations was 94.70% ± 1.25% standard error (SE), whereas the estimated cumulative success decreased to 89.78% ± 2.58 SE. Mechanical failures, including three zirconia framework fractures, two hairline cracks, nine chippings, and one delamination of the ceramic veneering, were recorded during the 1- to 5-year observation period. An odds ratio of 2.02 (95% confidence interval: 0.67 to 6.12) showed a moderate association between parafunction and failure.Zirconia-based tooth-supported FDPs showed promising clinical results over a period of up to 5 years. Technical complications were more commonly detected in patients with parafunctional habits.

PURPOSE The aim of this retrospective cohort study was to gather the outcomes of zirconia single crowns made by 16 members of the Italian Academy of Prosthetic Dentistry (AIOP) over a time period of up to 5 years. MATERIALS AND METHODS A total of 398 patients treated in private practices with 1,132 zirconia-based single-crown restorations made on natural teeth from January 2005 to July 2010 were included. Three hundred forty-three anterior restorations (30.3%) and 789 posterior crowns (69.7%) were made with 16 types of zirconia, using primarily chamfer or knife-edge tooth preparation, and examined according to the esthetic, functional, and biologic criteria. To evaluate the relationship of parafunction with mechanical failure, patients with clenching or bruxism were not excluded from the study group. RESULTS The cumulative survival rate of all restorations was 98.1%, while the cumulative success rate was 94.3%. Functional criteria had the highest number of failures. The odds ratio (OR) for all restorations was calculated to clarify the relationship between patients who were subject/not subject to parafunctions and technical complications; the OR was 2.60. An association between parafunction and mechanical failure was found in patients with severe parafunction. CONCLUSIONS Porcelain-veneered zirconia single crowns with chamfer and knife-edge preparations showed good clinical results over a period of up to 5 years. Technical complications were few and were limited primarily to patients with parafunction.