[The clinical analysis on the effects of different difficulty in root canal preparation].

Objective: To investigate the effects of root canal preparation treated by endodontists of different levels in different difficulty associated with the root canal anatomy factors.

Methods: Totally 422 teeth with 901 root canals were randomly selected from the Conservative Dentistry Department, West China Stomatology Hospital, and these teeth were respectively treated by junior specialist postgraduates, senior specialist postgraduates and endodontic specialists. Grading criteria of root canal risk factor and root canal therapy difficulty assessment were found based on 6 items: Tooth type, working length, root curvature, calcification, number of canals, and the previous endodontic treatment.