5-Year Clinical Outcomes of Three-Unit Posterior Zirconia- Ceramic Fixed Dental Prostheses: A Randomized Trial Comparing Manually and CAD/CAM Layered Veneering.

AIM: This randomized controlled trial compared the 5-year survival and complication rates of three-unit fixed zirconia dental prostheses (FDPs) veneered with CAD/CAM ceramic (group CAD) versus manually layered ceramics (group LAY). MATERIAL AND METHODS: Conducted at the University of Zurich, the study enrolled 57 patients requiring posterior FDPs, randomized to either group CAD or LAY. The CAD group received zirconia frameworks veneered with CAD/CAM-fabricated lithium disilicate ceramic, while the LAY group had manually veneered feldspathic ceramic. Follow-ups occurred at 6 months, 1, 3, and 5 years, with evaluations of survival, technical and biological complications. Categorical variables, such as technical and biological outcomes based on modified USPHS criteria, were analyzed using chi-squared tests or Fisher's exact tests to determine significant differences between the test and control groups. Survival and success rates of FDPs were estimated using Kaplan-Meier survival analysis, and the log-rank test was used to compare survival curves between the two groups. Statistical significance was set at p < 0.05. RESULTS: After 5 years, survival rates were 95.7% for LAY and 88.1% for CAD, with no significant difference. Technical and biological complications were similar across groups. Chipping, which presents one of the observed technical complications, was more extensive in the LAY group, whereas CAD group chippings were smaller and manageable by polishing. CONCLUSIONS: Both zirconia FDPs veneered with CAD/CAM lithium disilicate ceramic and manually layered feldspathic ceramic exhibit comparable 5-year survival and complication rates.