In vitro performance of violet LED and argon plasma with oxygen on dentin bleaching

This in vitro study aimed to evaluate the effect of violet LED and argon plasma, associated or not with oxygen, on chromatic alteration, whitening index, temperature variation, wettability, surface energy, total free interaction energy, and adhesive strength in dentin tissue. Thus, 100 bovine dentin discs were allocated to 5 groups (n=20): C - control; APL - argon plasma; APL+O - argon plasma + 3% oxygen; LED - violet LED; HP - 35% hydrogen peroxide. In the first bleaching treatment for each technique, chromatic alteration (ΔE00), bleaching index (ΔWID), and temperature variation were analyzed. Subsequently, the specimens were repolished, receiving the surface treatments again and designated for contact angle (o), surface energy (γs), and total free interaction energy (ΔG) analyses (n=5). In contrast, the remaining specimens were restored for bond strength analysis (n=15). From each specimen, four beams were obtained, two evaluated immediately and two after 10,000 thermal cycles. Bond strength data were subjected to 2-way repeated measures ANOVA, and the other analyses to 1-way ANOVA with Tukey's post hoc test (α=0.05). APL+O presented bleaching efficacy similar to the HP group, which, in turn, had the lowest bond strength values (p<0.05). LED was the only treatment that generated a temperature increase and showed a hydrophobic surface. APL+O presented lower contact angle values and higher ΔG values. APL and APL+O showed bond strength values that surpassed only those of the control group. It was concluded that plasma treatments were effective in dentin bleaching; however, none of the evaluated therapies managed to prevent the loss of bond strength.