8-year prospective clinical evaluation of posterior 3-unit zirconia-based FDPs

Objectives: The present prospective clinical study aimed at evaluating the clinical perfomances of tooth-supported 3-unit posterior zirconia FDPs after 8 years of service. Methods: Thirty-seven patients received 48 3-unit zirconia-based (Procera, NobelBiocare) FDPs. The prostheses replaced either a premolar or a molar. Specific inclusion criteria were used. Standardized tooth preparations were realized: 2mm occlusal reduction, 1.5mm axial reduction and circumferential chamfer shoulder placed 0.5 mm subgingivally buccally and supragingivally lingually on sound tooth structure; all internal angles were rounded. Impressions were made with polyethers (3M ESPE). CAD-CAM frameworks (Procera, NobelBiocare) with 9mm2 connector and 0.6mm retainer were made. The restorations were luted using a resin cement (RelyXUnicem, 3M ESPE). The patients were recalled after 1, 6 and 12 months after the cementation and then annually for a whole observational period of 8 years. Survival and success of the veneering ceramic and zirconia were assessed. The esthetic and technical outcomes were rated using the USPHS criteria. The biologic outcomes were analyzed at abutment and contralateral teeth. Descriptive statistics were performed (Kaplan-Meier, Wilcoxon). Results: All FDPs completed the study, resulting in 100% cumulative survival rate and 93.75% cumulative success rate. No losses of retention were recorded. Forty restorations were rated Alpha in all measured parameters. Minor chipping of ceramics was detected in 3 restorations. Four restorations were rated Bravo for marginal integrity at 8 years. No significant differences between the periodontal parameters of the test and control teeth were observed. As to esthetics, 42 restorations were rated Alpha and 6 were rated Bravo by both the clinicians and the patients at the 8-year follow-up. Conclusions: Eight-year clinical results showed that posterior 3-unit zirconia-based FDPs can be considered a viable treatment option in the medium-term. These restorations may be considered reliable to replace a posterior missing tooth.