Ultrastructural Alterations and Physical Changes on Bovine Dentin After Internal Bleaching with 35 % Hydrogen Peroxide

Abstract

The aim of the study was to investigate the effect of internal bleaching on physical proprieties and ultrastructure of the bovine dentin.40 bovine incisors were used, divided in four experimental groups: control group, composed by teeth that did not receive the bleaching agent (G1); teeth submitted to a single internal bleaching session (G2); teeth submitted to two internal bleaching sessions (G3); teeth submitted to three internal bleaching sessions (G4). In each of the sessions, 35 % hydrogen peroxide was applied for 45 minutes on the dentin surface. Tests were performed (microhardness and roughness) and were analyzed using one-way analysis of variance (ANOVA) and Tukey's post-hoc test (p≤0.05). Electromicrographs were captured for quality analysis. In the analysis of the superficial microhardness of the dentin, the internal bleaching reduced the Knoop microhardness since the first session, being observed statistically significant differences between the experimental groups and the control. The surface roughness gradually increased in the G2, G3 and G4 groups, but only G4 presented a statistically significant difference from the others. The qualitatively evaluated electromicrographs showed damage to the dentin ultrastructure, with areas of erosion and greater involvement of the intertubular when compared to peritubular dentin. Internal bleaching with 35 % hydrogen peroxide caused injuries in bovine dentin from the first treatment session. Both modifications in physical properties and dentin ultrastructure have been identified. These changes were intensified the higher the number of dentin internal bleaching sessions was exposed.