Influence of Er:YAG laser activation and hydrogen peroxide concentration on esthetic efficacy, peroxide kinetics, diffusion, and thermal response during dental bleaching

Background Laser-assisted in-office bleaching has been proposed to enhance whitening efficacy by accelerating hydrogen peroxide (H₂O₂) degradation and optimizing oxidative reactions. Nevertheless, Er:YAG laser influence on thermal behavior, peroxide kinetics, optical performance, and trans-amelodentinal diffusion remains insufficiently elucidated. Thus, this in-vitro study evaluated the combined effects of Er:YAG laser activation and different H₂O₂ gel concentrations on thermal, chemical, and optical responses during enamel bleaching. Methods 186 bovine incisors were allocated into six groups according to H₂O₂ concentration (9%, 17.5%, and 35%) and Er:YAG irradiation (with or without activation). Phase I assessed temperature at the enamel surface and pulp chamber, and H₂O₂ degradation at distinct evaluation periods. Phase II evaluated chromatic alteration ( Δ E 00 ), whitening index (WI D ) in relation to established perceptibility and acceptability thresholds, and trans-amelodentinal diffusion of H₂O₂. Statistical analyses were performed using ANOVA followed by Tukey post hoc tests (α = 0.05). Results Higher H₂O₂ concentrations resulted in significantly greater Δ E 00 and WI D values; however, these effects were accompanied by increased temperature and peroxide diffusion. Notably, comparisons between the highest and lowest H₂O₂ gel concentrations, irrespective of laser irradiation, exceeded the established whitening perceptibility threshold. Er:YAG irradiation significantly accelerated H₂O₂ degradation and enhanced whitening outcomes compared with non-irradiated groups. Notably, laser activation reduced trans-amelodentinal peroxide diffusion across all evaluated H₂O₂ gel concentrations. Overall, reductions in temperature and H₂O₂ gel concentration were observed over time. Conclusions Er:YAG-assisted bleaching modulates peroxide degradation kinetics, enhances whitening efficacy, and influences thermal and trans-amelodentinal peroxide diffusion.