EFEITO DOS DIFERENTES INSTRUMENTOS DE NITI NA INCIDÊNCIA DE DEFEITOS NA DENTINA DURANTE A REMOÇÃO DO MATERIAL OBTURADOR: UM ESTUDO IN VITRO

Abstract

Objective: To assess the effect of different gutta-percha removal (RGP) methods on the occurrence of dentinal defects. Materials 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 filled with gutta percha and Sealapex sealer using the lateral condensation technique. Twelve other roots were left filled 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 25x 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 were observed in 46.6% of the root sections. No defects were observed in the unprepared canals (control, G1). Defects were detected in all other experimental groups (G2 to G9). All RGP protocols led to a greater incidence of partial cracks and craze lines compared to the unretreated group. However, statistically significant difference was found only for the R-Endo group (G5) (p<.05). Conclusions: All RGP methods were linked to dentinal defects during retreatment procedures. RGP with R-Endo system had a significant impact on microcracks and craze lines formation.