Characterization, efficacy, and safety of a low-concentration hydrogen peroxide hydrogel with MnO-doped Biosilicate®...

The aim of this study was to develop a bleaching hydrogel containing 6 %HP and Biosilicate®(BioS) doped with manganese oxide (MnO_BioS), irradiated with violet LED-light.

MnO was incorporated into BioS via the oxide fusion route, and BioS/MnO_BioS (0 % and 10 %wt) were combined with 6 %HP. Particles and gel's characterization (n = 5), bioactivity assay (FTIR), photocatalytic evaluation (MB/ppm), HP decomposition rate (%), and pH evaluation were performed. Enamel/dentin blocks (n = 10) were treated: 35 %HP (positive control), 6 %HP gels BioS/MnO_BioS (0 % and 10 % wt), irradiated or not with LED. Bleaching was performed in three 30-min sessions at 7-day intervals. Specimens were evaluated for color change (ΔE₀₀), whiteness index (ΔWI_D), surface hardness recovery (%SHR), carbonate and phosphate (CO₃²⁻/PO₄³ ⁻) ratio in enamel before (T₀) and after treatments (T₁), and surface morphology at T₁. Data were analyzed by two-way ANOVA with Tukey's post-hoc (α = 0.05).

6 %HP_MnO_BioS_LED increased gel photocatalysis, HP decomposition, and pH when compared to 6 %HP and 35 %HP (p < 0.05). 6 %HP_MnO_BioS_LED showed statistically similar results to 35 %HP in ΔE₀₀, ΔWI_D, Δa, Δb, and ΔL (p < 0.05). The 35 %HP and 35 %HP_LED showed the lowest %SHR, followed by the 6 %HP and 6 %HP_LED BioS and MnO_BioS-containing groups showed higher carbonate/phosphate ratios compared to the other groups (p < 0.05).

The groups containing MnO_BioS and BioS, regardless of LED-light irradiation, exhibited higher %SHR and carbonate/phosphate ratio compared to 35 %HP and 35 %HP_LED. Additionally, 6 %HP_MnO_BioS_LED increased gel pH, photocatalysis, HP decomposition and exhibited bleaching efficacy similar to 35%HP.

This approach provides a safer alternative to 35 %HP gels, achieving superior bleaching outcomes with six times lower concentration of HP, while enhancing enamel calcium and phosphate levels and preserving mineral integrity.