The main goal of orthograde root canal retreatment is to completely remove the root canal content and chemically treat the residual infection. Purpose: The aim of this study was to evaluate the effectiveness of D-Race retreatment files supplemented with XP-Endo Finisher R in the removal of root canal filling material from oval-shaped canals. Methodology: Twelve mandibular incisors initially shaped with XP-Endo Shaper and filled by warm vertical compaction were consistently retreated with D-Race files and XP-Endo Finisher R. Micro-CT images were used to evaluate the quality of the root canal filling and the amount of remaining filling material after the two retreatment procedures. Results: The largest amount of root canal filling was removed at full canal length after using each of the retreatment systems. Significant difference was registered between the accumulated effect of the retreatment with D-Race and XP-Endo Finisher R and the volume of the initial filling material at full canal length (p<0.001). Insignificant difference in the amount of remaining filling material was found after using the supplementary retreatment system (p>0.05). The XP-Endo Finisher R file was almost equally efficient in the different portions of the canals but was still most productive apically. Conclusions: The additional application of XP-Endo Finisher R after the D-race retreatment files removed a significant amount of root canal filling. The combined use of the two retreatment systems did not result in completely clean root dentin walls.