Effectiveness of a hand file and three nickel-titanium rotary instruments for removing gutta-percha in curved root canals during retreatment

Objective. This study intended to compare the effectiveness of hand files and FlexMaster, ProTaper, and RaCe rotary instruments for removing gutta-percha in curved root canals during retreatment. Study design. Sixty curved mandibular premolars were randomly divided into 4 groups of 15 specimens each. The canals were enlarged and obturated using lateral condensation technique. After repreparation with the test instruments the specimens were cleared. The area of remaining obturation material was measured from 2 directions. Statistical analysis was performed using the Kruskal-Wallis test and a closed test procedure. Results. RaCe instruments revealed significantly less residual obturation material than FlexMaster files (P < .05). No significant difference was found among the hand file, ProTaper, and FlexMaster groups (P > .05). There were 5 fractured instruments in the ProTaper group and 3 in the FlexMaster group. Conclusion. The RaCe system is an efficient and safe device for gutta-percha removal in curved root canals.