Abstract
Objective: This ex vivo study compared the efficacy of Mtwo rotary and Reciproc reciprocating NiTi systems in removing gutta-percha from the mesiobuccal canals of human maxillary and mandibular first molars using cone-beam computed tomography (CBCT). Materials and Methods: Ninety mesial roots from extracted maxillary and mandibular firs molars were included. Each root presented a closed apex and a curvature angle of ˂ 20°. The crowns were sectioned at the CEJ, and the canal lenghths were standardized to 12 mm. he canals were prepared and obturated with gutta-percha and AH26 sealer using lateral condensation technique. Samples were randomly assigned to two retreatment groups: Mtwo (multi-file rotary system) and Reciproc (single-file reciprocating system). Gutta-percha removal followed standardized protocols, with CBCT imaging performed pre- and post-retreatment. Residual filling materials were evaluated at 2.5, 5, and 7 mm from the apex. Statistical analysis was conducted using chi-square and Wilcoxon tests. Results: Complete removal of obturation materials was not achieved by either system. Residual material in the Mtwo group was 16.90%, 11.86%, and 7.45% at 2.5, 5, and 7 mm, respectively; in the Reciproc group, it was 24.61%, 19.83%, and 16.24%. No significant differences were observed at 2.5 and 5 mm (P ˃ 0.05), while Mtwo showed superior efficacy at 7 mm (P=0.042). Conclusion: Complete removal of gutta-percha was not achieved in any of the groups. Mtwo was more efficient in gutta- percha removal at 7-mm section. Moreover,the single‑file design of the Reciproc system was associated with procedural simplification