Hardware complications and failure of three-unit zirconia-based and porcelain-fused-metal implant-supported fixed dental prostheses: a retrospective cohort study with up to 8 years.

OBJECTIVE: The aim of the present study was to assess the hardware complications and survival of three-unit implant-supported zirconia-based fixed dental prostheses (IZ) and implant-supported porcelain-fused-metal fixed dental prostheses (IP). MATERIAL AND METHODS: The study is a retrospective cohort study with up to 8 years (mean 4.8 years) follow-up. Patients with conventional three-unit implant-supported fixed dental prostheses (without cantilever) in posterior area were reviewed. Hardware complications and survival rate were evaluated. Chi-Square test was used to test the difference between IZ and IP groups. RESULTS: Two hundred and thirty-seven patents (IZ : 112, IP : 125) with 279 three-unit restorations (IZ : 127, IP : 152) participated in the study. The overall survival rate was 95.3% in IZ group and 94.7% in IP group at implant-level and 94.6% in IZ group and 94.4% in IP group at subject-level. Veneer chipping was the most frequently seen complication (20.1%). Significant higher minor veneer chipping rate (Grade 1) was found in IZ group (P = 0.04). No significant difference of veneer chipping rate (Grade 2 and Grade 3) was found between the two groups. The overall hardware complication rates of IZ were significantly higher than IP (33.07% and 18.42%, P = 0.01). CONCLUSION: High survival rate of zirconia-base and Porcelain-fused-to-metal (PFM) restorations can be achieved with up to 8 years follow-up. The zirconia-based restorations need more polishing procedures, maintenance, and professional care than PFM restorations. The number of implants supporting a fixed dental prosthesis did not influence the implant survival and hardware complications. Well-designed studies with high evidence level are still needed to further explore the hardware complications and clinical survival of IZ and IP.