In vitro bleaching efficacy of violet LED associated with 10% hydrogen peroxide and 10% carbamide peroxide

•Violet LED plus 10% carbamide peroxide showed no enamel microhardness reduction.•Violet LED plus 10% peroxide-based agent was as efficient as 35% hydrogen peroxide.•Violet LED plus 10% peroxide-based agent showed color changes visible to human eyes. This in vitro study evaluated the efficacy and the effect over the dental enamel surface of violet LED dental bleaching associated to different concentrations of carbamide and hydrogen peroxide. Human dental blocks (n = 100) were randomly distributed into 5 groups: 10% hydrogen peroxide (HP10), 10% carbamide peroxide (CP10), 10% hydrogen peroxide with violet LED (VHP10), 10% carbamide peroxide with violet LED (VCP10) and 35% hydrogen peroxide (HP35). The specimens were analyzed by Vickers microhardness test (n = 50) initially, immediately after and seven days after ending the bleaching protocol. For color analysis (n = 50), the specimens were evaluated for bleaching effectiveness (ΔE2000, ΔE1976) and whiteness index (ΔWID) with EasyShade spectrophotometer, before bleaching protocol and seven days after ending the bleaching protocol. The microhardness and color data were analyzed using one-way ANOVA with post-hoc Tukey test (α = 0.05). The microhardness values showed difference among the investigated groups only immediately after the end of the dental bleaching (p