Effect of Solvent Use on Dentinal Integrity and Filling Removal During Endodontic Retreatment: A Micro-Computed Tomography Study

Introduction: This study evaluated, using micro-computed tomography (micro-CT), whether solvent use during endodontic retreatment influences dentinal defect formation and the removal of filling material compared with mechanical retreatment alone. Materials and methods: Twenty extracted human mandibular molars were prepared and obturated using standardized protocols and randomly allocated to solvent-assisted retreatment or retreatment without solvent (n=10 per group). Micro-CT scans were obtained before treatment, after obturation, and after retreatment at a voxel size of 13.68 μm. Dentinal defects were assessed using axial images, and residual filling-material volume was measured three-dimensionally in the apical, middle, and coronal thirds. Between-group comparisons were performed using the Welch independent-samples t-test or Mann-Whitney U test, as appropriate. Within-group comparisons were performed using the Friedman test. Results: No dentinal defects were detected in any specimen (0/20). However, the exact 95% confidence interval indicated that a low-incidence effect could not be excluded. Residual filling material was detected in all canals after retreatment. No significant differences were observed between the solvent-assisted and non-solvent groups in residual filling-material volume at any canal third after adjustment for multiple comparisons (all adjusted P>0.05). Conclusions: Under the conditions of this in vitro study, solvent use did not significantly improve filling-material removal compared with mechanical retreatment alone. No dentinal defects were detected in either group; however, the exploratory nature and limited sample size of the dentinal-defect analysis preclude excluding a low-incidence effect.