Comparative evaluation of three different retreatment files for gutta-percha removal under confocal laser scanning microscope: An in vitro study

Aim of the study: To compare the efficacy of different rotary instruments for removing obturating material from root canals in premolars measured radiographically using confocal laser scanning microscope. Materials and Methodology: Twenty-four extracted human premolars (N=24) were selected for the study. Standard endodontic access cavities were prepared using an SF-41 bur, and working length was established with a size 10 K-file (Mani). Biomechanical preparation was completed using NeoEndo Flex rotary files up to size 25/.06. Canals were irrigated with 2 mL of 2.5% sodium hypochlorite followed by saline after each instrumentation. Master gutta-percha cones of size 25/.06 with accessory cones were used for Obturation along with AH Plus sealer. All samples were dried with paper points and obturated; radiographic verification was conducted to confirm apical extent and adaptation. The teeth were then stored at 37°C and 100% humidity for two weeks to allow complete sealer setting. Samples were divided into three groups (N=8 each): Group A-Retreatment Endodontics Kit, Group B-Endostar ReVision, and Group C-Coltene HyFlex Remover. Retreatment was performed using the respective systems, with 2.5% sodium hypochlorite irrigation after each instrument change. Retreatment was deemed complete when no visible gutta-percha or sealer remained on instruments or in the irrigant. Total retreatment time was recorded using a stopwatch, and residual filling materials were evaluated under a confocal laser scanning microscope. Results: In all the groups Coltene Hyflex Remover retreatment files showed less remnants of the gutta-percha. The time taken for retreatment was significantly higher for Retreaty from Perfect Endo followed by Endostar revision files and Coltene Hyflex Remover retreatment files. Conclusion: Coltene Hyflex Remover files had less time taken and least amount of remnants during retreatment.