INTRODUCTION: The root curvature represents a challenge during the endodontic retreatment. Considering the different techniques to fill the root canals and the growing use of bioceramic sealers, this study aimed to evaluate the influence of the filling technique associated with a bioceramic sealer on the remaining filling material and the impact on the remaining dentin after the filling removal in the retreatment of curved mesial canals of mandibular molars. METHODS: Eighteen curved mesial roots of mandibular molars with Vertucci type IV canals were prepared up to instrument 35/.05. Two groups were established according to the filling technique: single-cone (n = 18) and continuous wave of condensation (n = 18). Bio-C Sealer was used for both techniques. The filling was removed using the Reciproc Blue R25 instrument, and the repreparation was carried out using the Reciproc Blue R40 instrument. The samples were scanned by micro-computed tomography before and after the filling removal and analyzed regarding the volume of the remaining filling material and dentin thickness for calculating transportation and centering ability. For statistical analysis, the data normality was checked, and parametric tests were used for normal distribution and nonparametric tests for nonnormal distribution. RESULTS: The remaining filling material was observed in both groups during retreatment, with no differences. Analyses of transportation and centering ability also indicated similarities between the two groups. CONCLUSIONS: Endodontic retreatment in curved mesial canals of mandibular molars filled with single-cone or continuous wave of condensation technique and bioceramic sealer was similar. The use of reciprocating instruments for filling removal and repreparation was efficient in curved mesial canals of mandibular molars, with no complications.