Evaluation of Zirconium-Oxide-Based Ceramic Single-Unit Posterior Fixed Dental Prostheses (FDPs) Generated with Two CAD/CAM Systems Compared to Porcelain-Fused-to-Metal Single-Unit Posterior FDPs: A 5-Year Clinical Prospective Study

Purpose: The purpose of this prospective clinical study was to determine the success rate of single-unit posterior fixed dental prostheses (FDPs) with zirconia copings generated with two CAD/CAM systems, compared to porcelain-fused-to-metal (PFM) single-unit posterior FDPs after 5 years of function. Materials and Methods: From 2005 to 2006, 60 patients who needed a single-unit FDP on a first molar in the mandibular jaw (left or right) in a private office setting were included in this study. The 60 first mandibular molars were randomly divided into three groups (n = 20): in the control group (group C), 20 PFM FDPs were included. In the other two groups CAD/CAM technology was used for the fabrication of the zirconium-oxide copings: 20 single-unit posterior FDPs with zirconia copings were generated with the Procera system (group P, Nobel Biocare); 20 single-unit posterior FDPs with zirconia copings were generated with the Lava system (group L, 3M ESPE). For the ANOVA follow-up data, the clinical life table method was applied. The statistical analysis was performed using two nonparametric tests, the log-rank test for k-groups and the Fisher exact test. Results: No statistically significant difference in the clinical outcome of zirconiaceramic FDPs of both groups (P and L) evaluated together and metalceramic posterior single FDPs was found at 5 years of function; however, clinical data showed that technical problems, such as extended fracture of the veneering ceramic, tended to occur more frequently in the zirconiaceramic FDP groups. The difference in the frequency of failure was statistically significant only in the comparison of groups C and P. Conclusions: Even if no statistically significant difference in the clinical outcome of zirconiaceramic FDPs of both groups (P and L) considered together and metalceramic posterior single FDPs was found at 5 years of function, clinical data showed that the two zirconiaceramic FDP groups tended to have more frequent clinical problems: for this reason all the clinical and technical variables related to the use of zirconiaceramic FDPs generated with CAD/CAM systems should be carefully considered prior to all treatment procedures.