Complete removal of old filling material is essential for successful endodontic retreatment. While a variety of techniques—such as hand files, rotary NiTi instruments, ultrasonic devices, and lasers—are available, none are fully effective, particularly in anatomically complex oval-shaped canals. Supplementary instruments have been introduced to improve outcomes. This study evaluated the efficacy of the XP-Endo Finisher R (XPEF-R) in removing root canal filling material after retreatment with three different NiTi rotary systems: ProTaper Universal Retreatment (PTUR), ProTaper Next (PTN), and WaveOne Gold (WOG). A total of 36 extracted mandibular incisors with single, straight, oval-shaped canals were standardized and initially prepared using the XP Endo Shaper system. The canals were obturated with gutta-percha and AH Plus sealer using warm vertical compaction. Specimens were divided into three groups (n=12) and retreated with PTUR, PTN, or WOG. Micro-CT scans were used to measure the volume of residual filling material. Following this, all samples underwent supplementary instrumentation with XPEF-R. Statistical analysis was conducted using the Kruskal-Wallis nonparametric test. The greatest volume of material was removed from the full canal length, though differences among canal sections were not statistically significant. PTUR showed the most effective performance across all levels. While XPEF-R further reduced residual material, the reduction was not statistically significant (p > 0.05). The PTUR and XPEF-R combination yielded the best results, but not significantly better than the other groups. In conclusion, the combination of the XP-Endo Finisher R with other rotary Ni-Ti systems is effective for the retreatment of oval-shaped canals, with the ProTaper Universal Retreatment system being superior.