Impact of different gutta-percha removal techniques on dentinal integrity: an in vitro analysis

Background: This study aimed to evaluate the impact of different gutta-percha removal (GPR) techniques on the occurrence of dentinal defects in bovine root canals. Material and Methods: One hundred and eight bovine incisors were selected and stored in distilled water. The crowns were removed, leaving roots approximately 17 mm in length. Twelve roots were left unprepared and served as control (G1), and the remaining 96 roots were instrumented with BioRace files up to size 40/.04 (BR5) and f illed with gutta-percha and Sealapex sealer using the lateral condensation technique. Twelve other roots were left f illed and received no retreatment procedure (G2). The remaining 84 roots underwent filling material removal with R-Endo (G3), D-Race (G4), WaveOne Gold (G5), ProTaper Retreatment (G6), Mtwo R (G7), Reciproc (G8) instruments or with R1-Clearsonic ultrasonic insert (G9). After GPR, final apical enlargement was achieved using a BR7 (#60/.02) instrument. Roots were sectioned 3, 6 and 9 mm from the apex and observed under a stereomicroscope at 25ᵡ magnification. The presence/absence of root fractures, microcracks, and craze lines were recorded. Chi-square tests compared the incidence of dentinal defects between the groups, with a significance level set at P<.05. Results: Defects occurred in 46.6% of the samples. No defects were observed in the unprepared canals (control, G1). Defects were detected in all other experimental groups (G2 to G9). Among retreatment techniques the R-Endo group (G3) presented significantly higher microcracks and craze lines (P<.05). Defects were more frequent in the coronal and middle thirds. Conclusions: All GPR methods were linked to dentinal defects. The R-Endo system significantly increased microcracks and craze lines.