The effects of two different heat-treated rotary file systems and ultrasonic activation on canal retreatment: a micro-computed tomography study

2. ABSRACT The Effects of Two Different Heat-Treated Rotary File Systems and Ultrasonic Activation on Canal Retreatment: A Micro-Computed Tomography Study The aim of our study is to evaluate the effect of two different Ni-Ti rotary file systems and additionally passive ultrasonic irrigation (PUI) on the amount of remaining root canal filling material in the retreatment of mandibular premolar teeth, using Micro-CT imaging. In the present study, forty extracted single-rooted, single-canal premolar teeth with oval canal morphology due to periodontal or orthodontic reasons were utilized. After verifying the apical patency with #10 K-file, the root canals were shaped up to F2 size using ProTaper Gold (PTG, Dentsply Sirona, Ballaigues, Switzerland) Ni-Ti rotary file system. The root canals were then filled with AH Plus sealer and gutta-percha cones using cold lateral compaction technique. Temporary filling material was applied to seal the root canals, and the specimens were stored in an environment with 37°C and 100% humidity for 30 days. Prior to the removal of root canal filling material, Micro-CT scanning was performed to evaluate the volume of the filling material. For the removal of filling material, the teeth were randomly divided into four groups (n=10): Group I: Reciproc Blue (RB, VDW, Munich, Germany), Group II: MicroMega Remover (Coltene/Whaledent, AG, Altstätten, Switzerland), Group III: Reciproc Blue + PUI, and Group IV: MicroMega Remover + PUI. After completion of canal retreatment procedures, the remaining filling material was assessed through second Micro-CT scans. The acquired data before and after the procedures were evaluated using 3D modeling technique, and the percentage of remaining filling material was calculated. Reciproc Blue showed a statistically significant difference in the amount of remaining filling material compared to Reciproc Blue + PUI, whereas MicroMega Remover exhibited a statistically significant difference when compared to MicroMega Remover + PUI (p<0.05). Additionally, a statistically significant difference was observed between groups with and without PUI application (p<0.05). Keywords: Root canal retreatment, Micro-CT, remaining filling material, Reciproc Blue, MicroMega Remover, Passive Ultrasonic Irrigation