Abstract: Objective: To evaluate the efficiency of Waveone Gold and Reciproc Blue in removing filling materials from oval-shaped and differently curved root canals. Methods: 150 extracted human premolars with single root canal were divided into three groups according to their curvature, i.e straight canal group, moderate bending group, and severe bending group. There were 50 teeth in each group. After the completion of canal preparation and filling, each group was randomly divided into five subgroups (n=10), respectively. H file, ProTaper Universal Retreatment, Mtwo R, Waveone Gold, and Reciproc Blue were used to remove the root canal filling materials. Time and complication were recorded and the residual materials in the root canal wall were evaluated. Results: The operation time of H file was significantly longer than other groups and the whole residual amount of H was also significantly more than other groups (P＜0.05). There was no statistical difference among other machine file groups. There was 1 case of Mtwo R file separation in moderate bending group and 2 cases of Mtwo R files in severe bending group. Conclusion: Recioproc Blue and Waveone Gold could effectively remove filling materials, which showed better safety in curved oval root canals.

Key words: root canal retreatment, removal of filling materials, Reciproc Blue, Waveone Gold