Randomized Controlled Clinical Trial to Compare Posterior Implant-Supported Modified Monolithic Zirconia and Metal-Ceramic Single Crowns: One-Year Results

Purpose The purpose of this randomized controlled clinical trial was to investigate the prosthetic outcomes of posterior implant-supported single crowns (SCs) with a modified monolithic zirconia or metal-ceramic design at 1 year of loading. Materials and Methods Forty participants with 73 dental implants in need of at least 1 maxillary or mandibular posterior implant-supported SC were consecutively selected for this study. The included participants were randomly divided into modified monolithic zirconia (MMZ) and metal-ceramic (MC) groups. The implant-supported SCs were examined after 1 year for survival and technical complications. Descriptive statistics were used to illustrate the data, and the association associated risks of complications were estimated using the logistic regression model with Firth's approach for rare outcome (alpha = 0.05). Results During the observation period, 2 participants in the MC group were lost to follow-up. A total of 38 participants with 70 posterior implant-supported SCs (36 and 34 SCs in the MMZ and MC groups respectively) completed the 1-year follow-up examination. One implant failed in the MMZ group. The 1-year survival rates for implants and crowns were both 97.2% in the MMZ group. The survival rates for implants and crowns were both 100% in the MC group. One screw loosening event was observed in one screw-retained SC in the MMZ group; however, 8 complication events occurred in 7 SCs in the MC group. Therefore, the complication-free rates were 97.1% and 79.4% in the MMZ and MC SCs respectively. The most common complication in the MC group was screw loosening (14.7%), followed by loss of retention (5.9%), and ceramic fracture (2.9%). Significantly more technical complications were observed in the MC SCs than MMZ SCs (p = 0.0432). Conclusion The modified monolithic zirconia design applied to the posterior implant-supported SCs had a significantly lower technical complication rate than did the metal-ceramic one.