Clinical Evaluation of Cement-Retained Implant-Supported CAD/CAM Monolithic Zirconia Single Crowns in Posterior Areas: Results of a 6-Year Prospective Clinical Study

Background: Different technologies and materials can be used for implant-supported restorations in posterior areas. Our study aimed to evaluate the clinical performance of CAD/CAM implant-supported monolithic zirconia single crowns (ZrSCs) cemented onto titanium abutments with a dual-curing resin cement after 6 years of use. Methods: Fifty patients in need of one single crown in posterior regions were enrolled. The patients were recalled for a follow-up after 6 months and then yearly for a total observation period of 6 years. The biological and technical complications were examined using criteria set by the United States Public Health Service (USPHS), whereas visual analogue scales (VASs) were used to evaluate the patients' aesthetic and functional satisfaction. Results: No patient was lost at follow-up; both the survival and success rates were 100%. No fractures, decementation, peri-implantitis, or soft tissue inflammation were recorded. Forty-six restorations were rated Alpha in each evaluated parameter of the USPHS's criteria. According to the patients' VASs assessments, the overall function of the ZrSCs was 8.4 (+/- 2.1), whereas the overall aesthetic was 8.7 (+/- 0.7). Conclusions: Monolithic zirconia single crowns cemented with dual-curing resin cements onto titanium abutments can be considered an effective clinical option in posterior regions after 6 years of function.