Abstract: Objective To evaluate the effect of ferrule length on the survival of residual crown and roots restored with prefabricated fiber post and core system. Methods 68 defect teeth of residual crown and roots from 56 patients were collected in this study. After prefabricated fiber post and core restoration,all teeth were prepared with different ferrule lengths (0~1 mm,1~2 mm,more than 2 mm) and restored with ceramic crowns. The success rate of prostheses was observed after 2 to 5 years and the data was analyzed by χ2 test. Results The success rates for roots with the ferrule length among 0~1 mm,1~2 mm and more than 2 mm were 60% (12/20),96.8% (30/31) and 100% (17/17) respectively. There were significant differences between roots with ferrule length of 0 to 1 mm and roots with ferrule length of more than 1 mm(P＜0.05). Conclusions More than 1 mm ferrule length will significantly increase the success rate of pulpless residual roots. 

Key words: post and core, prefabricated fiber post, ferrule, residual crown and root