Objective This study aimed to evaluate the success and survival rate of endodontically treated premolars restored by ceramic onlays by comparing restored by quartz fiber posts and metal ceramic crowns.Methods Ninety-four patients with 126 endodontically treated premolars were enrolled in this study and divided into 4 groups according to the remaining axial walls and restorative methods. The observation time was 36 months. The success and survival rates of the restorations, as well as causes of failures, were analyzed.Results At the final follow-up, the success and survival rates of the mild defect endodontically treated premolars were restored by quartz fiber posts and the crowns were at 96.3% and 98.1%; the success and survival rates of the severe defect premolars restored by quartz fiber posts and crowns were at 88.5% and 96.2%. The success and survival rates of the mild defect premolars restored by cast ceramic onlays were both at 96.6%, the success and survival rates of the severe defect premolars restored by cast ceramic onlays were at 94.1% and 100%, respectively. The success and survival rates of the different groups were no significant difference (P>0.05).Conclusion Based on the results and within the limits of this study, cast ceramic onlays is a very reliable method to restore endodontically treated premolars.
