Comparative Evaluation of Automated Retreatment Systems for Bioceramic Sealer Removal: An In Vitro Scanning Electron Microscopic Study.

BACKGROUND: Calcium silicate-based bioceramic sealers have gained widespread acceptance because of their excellent sealing ability and biocompatibility. However, their strong adhesion to dentinal walls poses a significant challenge during nonsurgical endodontic retreatment. This study evaluated and compared the efficacy of the Neoendo Retreatment (Neoendo, Orikam Healthcare India Pvt. Ltd., Gurugram, India), ProTaper Universal Retreatment (Dentsply Sirona, Ballaigues, Switzerland), and HyFlex Remover (COLTENE/Whaledent AG, Altstätten, Switzerland) file systems in removing bioceramic sealers from root canal walls using scanning electron microscopy (SEM). MATERIALS AND METHODS: This in vitro study evaluated 45 extracted human mandibular premolars obturated with a calcium silicate-based bioceramic sealer and thermoplasticized gutta-percha. After standardized root canal preparation and obturation, the specimens were randomly allocated into three groups (n = 15) according to the retreatment system used: Neoendo Retreatment, ProTaper Universal Retreatment, and HyFlex Remover. Following retreatment, the roots were longitudinally sectioned and examined under scanning electron microscopy (SEM) at ×1000 magnification. The presence of residual bioceramic sealer in the coronal, middle, and apical thirds was assessed using the modified Ezzie scoring system. Data were analyzed using the Friedman and Kruskal-Wallis tests, followed by Dunn's multiple comparisons test, where appropriate, with statistical significance set at p < 0.05. RESULTS: All three retreatment systems left residual bioceramic sealer on the canal walls, and none achieved complete removal. Within each retreatment system, residual bioceramic sealer scores differed significantly among the coronal, middle, and apical thirds (Friedman test, p < 0.05). Dunn's post hoc analysis demonstrated significantly higher residual sealer scores in the apical third than in the coronal third, whereas no significant differences were observed between the coronal and middle thirds or between the middle and apical thirds. Intergroup comparisons revealed no statistically significant differences among the Neoendo Retreatment, ProTaper Universal Retreatment, and HyFlex Remover systems at any root canal level (p > 0.05), although the HyFlex Remover system showed a trend toward lower residual sealer scores. SEM analysis demonstrated region-specific differences in canal cleanliness, characterized by cleaner dentinal surfaces in the coronal third and greater residual bioceramic sealer with marked dentinal tubule occlusion in the apical third. CONCLUSION: Neoendo Retreatment, ProTaper Universal Retreatment, and HyFlex Remover exhibited comparable efficacy in bioceramic sealer removal. Complete sealer removal remains unattainable, particularly in the apical third, highlighting the need for adjunctive cleaning strategies to improve the retreatment outcomes.