Performance of Bonded Lithium Disilicate Partial-coverage Crowns in the Restoration of Endodontically Treated Posterior Teeth: An Up to Seven-Year Retrospective Study

SUMMARY Objectives: To evaluate the clinical performance of adhesively bonded lithium disilicate glass-ceramic (LDG) partial-coverage crowns in restoring posterior endodontically treated teeth (ETT). Methods and Materials: A total of 121 morphologically compromised posterior ETT were restored with LDG partial-coverage crowns between October 2015 and January 2018. The restorations were fabricated in the laboratory or at the chairside. Two adhesive systems and resin cements were used to cement the restorations. Tooth and restoration survival rates were calculated. The restorations were evaluated clinically using the modified United States Public Health Service (USPHS) criteria for an observation period of 5-7 years. The Cox proportional hazards model was used to estimate relative failure risks such as tooth type, resin cements, gender, and sleep bruxism. The standard chi-squared test was used to compare the survival of different tooth types for significant differences (α=0.05). In addition, survival probability was calculated using the Kaplan–Meier algorithm. Results: Among seven failed cases, one was a tooth fracture, and six were restoration fractures. According to the Kaplan–Meier analysis, the estimated survival rate of the teeth was 99% for seven years, while the estimated survival rate of the restorations was 94.8% for 5 years and 92.8% for 7 years. Tooth type and resin cements did not influence restoration survival rates (p>0.05), while sleep bruxism and male patients might increase the risk of failure (p<0.05). Conclusions: The indirect adhesively bonded LDG partial-coverage crowns of posterior ETT exhibited favorable clinical outcomes. Ceramic fracture was the most common failure pattern.