The Effects of Mtwo, R-Endo, and D-RaCe Retreatment Instruments on the Incidence of Dentinal Defects during the Removal of Root Canal Filling Material

Introduction: The aim of this study was to compare the incidence of dentinal defects after retreatment procedures with different nickel-titanium rotary retreatment files. Methods: One hundred-eighty mandibular premolars were randomly assigned to 6 groups (n = 30 teeth per group). One group was left unprepared, and the remaining 5 groups were prepared with K-files (Dentsply Maillefer, Ballaigues, Switzerland) and filled with gutta-percha and AH plus sealer (Dentsply Maillefer, Ballaigues, Switzerland). Of these 5 groups, 1 group was left filled and received no further treatments; in the other groups, removal of the filling material was performed with Mtwo R (VDW, Munich, Germany), D-RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland), R-Endo instruments (Micro-Mega, Besancon, France), or Hedstrom files (Dentsply Maillefer). Roots were then sectioned 3, 6, and 9 mm from the apex and observed under a microscope. The presence of dentinal defects was noted. Chi-square tests were performed to compare the incidence of dentinal defects between the groups. A Pearson correlation test was performed to check the correlation between defects and root level or remaining dentin thickness. Results: No defects were observed in the unprepared group. Dentinal defects were detected in all retreatment groups. Retreatment, groups showed significantly more defects than the filled but no retreatment group (P .05). There was no correlation between the appearance of defects and level of the root or remaining dentin thickness. Conclusions: Under the experimental conditions, all retreatment techniques used in this' study created defects in the root dentin