Evaluation of bleaching efficacy and cytotoxicity of an experimental hydrogel containing MnO-Doped Biosilicate® activated by violet LED light

Abstract

Although hydrogen peroxide (HP) at 35% is effective in dental bleaching, the cytotoxicity associated with its use remains a significant concern. In this context, this study aimed to develop a bleaching hydrogel containing 6% HP, Biosilicate® (BioS) doped with manganese oxide (MnBioS), and irradiated with violet LED light (LED). Enamel/dentin discs were submitted to the following bleaching treatments (n=08): 35%HP (positive control), 6%HP gel containing BioS or MnBioS (0 and 10 wt%), with or without LED irradiation. The discs were adapted to artificial pulp chambers (APCs), with the enamel exposed for bleaching and the dentin facing the culture medium (DMEM). Bleaching was performed in three 30-minute sessions with 7-day intervals. After bleaching, the extracts (DMEM + bleaching gel components diffused through the discs) were collected and applied to the odontoblast-like MDPC-23 cells. Color change (ΔE₀₀) and changes in the whiteness index (ΔW₀₀) were determined before (T₀) and after the last bleaching session (T2). Cell viability (MTT, %), HP diffusion (µg/mL), oxidative cell stress (OxS), and cell fluorescence (live/dead assay, by confocal microscopy) were assessed after the first session (T₁). The data were analyzed using ANOVA and Tukey's test (p=0.05). The addition of 6%HP₍MnBioS₎₍LED₎ exceeded ΔW₀₀ compared to 35%HP, showing statistical differences from the other groups, while ΔE₀₀ was statistically similar to 35%HP. 6%HP₍MnBioS₎₍LED₎ demonstrated higher cell viability, lower HP diffusion, and reduced oxidative stress (OxS) compared to the other groups (p<0.05). 6%HP₍MnBioS₎₍LED₎ increased bleaching potential and presented lower cytotoxicity compared to 35%HP.