LAUSR

Objective The aim of this study was to evaluate the efficacy of supplementary techniques (ultrasonic tip/XP-endo Finisher R) in removing remaining filling materials (gutta-percha/AHPlus/BCSealer) from oval-shaped root canals during non-surgical endodontic retreatment. Material and methods Twenty-eight distal roots of human mandibular molars with single and oval-shaped canals were initially shaped with a R40 instrument and filled with gutta-percha points and AH Plus ( n  = 14) or BC Sealer ( n  = 14) followed by an initial micro-CT scanning. Initial filling material removal was performed in all 28 samples with an R50 instrument, and all samples submitted to a second micro-CT. Supplementary techniques with ultrasonic tips or XP-endo Finisher R instruments were performed in each sealer group, and all samples submitted to a third micro-CT. The volume of remaining filling material was calculated for the entire canal as well as for the coronal, middle, and apical thirds. Statistical analyses were performed using T, ANOVA 3-way, and Tukey tests. Results Lower values of remnant filling material were found for BC Sealer (16.06 ± 14.34) compared to AH Plus (28.30 ± 10.54) ( P  < 0.001), and considering the supplementary technique, lower values of remnant filling material were found for the ultrasonic tip (18.95 ± 11.05) compared to XP-endo Finisher R (25.41 ± 15.81) ( P  = 0.025). Ultrasonic instruments significantly reduced the percentage of remaining filling material for both AH Plus ( P  = 0.04) and BC Sealer ( P  = 0.02) while XP-endo Finisher R was effective for AHPlus only ( P  = 0.04). The remaining filling material was observed in all samples regardless the filling material or the supplementary technique employed. Conclusions Supplementary techniques increased filling material removal; however, none of them was able to render root canals completely free from root fillings. Ultrasonic tips should be considered a good option for endodontic retreatment, especially for bioceramic cases. Clinical relevance Supplementary instrumentation techniques are effective tools to reduce the amount of filling materials during root canal retreatment.