Impact of Violet LED Light and High-Concentration Hydrogen Peroxide on Dentin Mechanical Properties, Collagen, and Enzymatic Activity

ABSTRACT Objective: Because the application of violet light-emitting diode (LED) light may enhance the release of reactive oxygen species, and its combination with a high-concentration bleaching agents may accelerate collagen degradation, this study aimed to evaluate its impact on the mechanical properties of demineralized dentin matrix exposed to high or low concentrations of hydrogen peroxide used in in-office treatments. Methods: The evaluation included changes in mass, modulus of elasticity, ultimate tensile strength, hydroxyproline release, and total matrix metalloproteinase (MMP) activity. Demineralized collagen matrices were assigned to groups (n = 10): 35% hydrogen peroxide, 7.5% hydrogen peroxide, or simulated body fluid (SBF, control) with or without violet LED light. Treatments were conducted over three 30-minute sessions. During each session, violet LED light was applied in 20 cycles of 60 seconds of light, followed by a 30-second rest interval. Dentin matrix mass variation, modulus of elasticity, ultimate tensile strength after treatments, and hydroxyproline release were evaluated. Additionally, other dentin collagen matrices were evaluated for total MMP activity before and after the bleaching protocols (n = 10). Results: Violet LED light caused a significant mass loss in the 35% hydrogen peroxide group ( p = 0.007; Mann-Whitney test) compared to the other treatments. There were no significant treatment-related differences in modulus of elasticity ( p = 0.527; generalized linear models). The 35% hydrogen peroxide group showed lower ultimate tensile strength and higher hydroxyproline release than the 7% hydrogen peroxide and control groups ( p < 0.0001; generalized linear models). All experimental groups exhibited lower percentages of MMP inhibition than the control inhibitor group ( p < 0.0001; generalized linear models). Conclusions: Violet LED light and different in-office bleaching agent concentrations did not reduce the modulus of elasticity. Violet LED light combined with 35% hydrogen peroxide reduced dentin mass and ultimate tensile strength, and increased hydroxyproline release and total MMP collagen activity.