Introduction: The aim of this study was to estimate the remaining amount of residual filling materials in root canals after retreatment using ProTaper Universal Retreatment (PTUR) files (Dentsply Maillefer, Ballaigues, Switzerland) alone or with the additional use of the Self-Adjusting File (SAF; ReDent-Nova, Ra'anana, Israel), Reciproc (VDW, Munich, Germany), or Hedstrom-files (H-file; VDW, Antaeos, Munich, Germany) with volumetric estimation using the stereo logic method via cone-beam computed tomographic images. Methods: Forty-eight mandibular premolars with single canals were used. The canals were instrumented with ProTaper rotary instruments up to F4 and filled with gutta-percha and AH26 sealer (Dentsply De Trey, Johnson City, TN). All the samples were placed into the silicone models. Samples were scanned with cone-beam computed tomographic imaging and assigned into 4 groups (n = 12) according to retreatment files: the PTUR system group, the PTUR system plus SAF group, the PTUR system plus Reciproc group, and the PTUR system plus H-file group. The specimens were rescanned after retreatment procedures, and the volume estimations of the remaining filling materials were performed using the stereologic method. Data were analyzed using Kruskal-Wallis and Dunn tests. Results: There was no significant difference among the groups regarding mean percentage volumes of the filling materials before retreatment procedures (P > .05). None of the retreatment procedures provided complete removal of the filling materials. The additional use of the SAF did not significantly improve the removal of filling materials when compared with the PTUR system alone (P > .05). However, the additional use of Reciproc or hand H-files significantly improved the removal of filling materials when compared with the PTUR system alone (P < .05). Conclusions: The additional use of files with different motion kinetics improved the removal of root canal fillings; however, none of the systems completely removed the root canal filling material from the root canals.