Objective To assess the clinical effect of rotary ProTaper in preparation of root canal during retreatment. Methods A total of 120 teeth which needed endodontic retreatmemt were selected and randomly divided into 2 groups with 60 teeth in each group. The root canals were prepared with rotary ProTaper and crown-down technique in experimental group（PT） and K-files with step-back technique in control group（HF）, respectively. And both filled with cold lateral condensation technique. To record the prepared time and numbers of postoperative complications, and according to X-ray of pre-therapy and post-therapy to estimate the effect of root canal preparation and filling. Results The time of preparation in PT group was obviously shorter than HF group. The
effect of root canal shaping and filling in PT group was better than that in HF group. There were 3 fractured instruments in PT group. Conclusion Rotary ProTaper showed high performance, better shaping ability and effective
obturation, but we should pay attention to prevent instrumental fracture.
