Effect of a novel low-concentration hydrogen peroxide bleaching gel containing nano-sized sodium trimetaphosphate and...

To evaluate in vitro the effects of nano-sized sodium trimetaphosphate (TMPnano) and sodium fluoride (F) added to a 17.5 % hydrogen peroxide (H₂O₂) bleaching gel on the color change, enamel mechanical and morphological properties, and H₂O₂ transamelodentinal diffusion.

Bovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 17.5 % H₂O₂ (17.5 % HP); 17.5 % H₂O₂ + 0.1 % F (HP/F); 17.5 % H₂O₂ + 1 % TMPnano (HP/TMPnano); 17.5 % H₂O₂ + 0.1 % F + 1 % TMPnano (HP/F/TMPnano) and 35 % H₂O₂ (35 % HP). The gels were applied for 40 min on three sessions, each session spaced 7 days apart. The total color change (ΔE*_ab) according to the Commission Internationale de l'Eclairage (CIE) L*a*b* color change measured by CIEDE2000 (ΔE₀₀), whitening index (ΔWI_D), surface hardness (SH), surface roughness (Ra), cross-sectional hardness (ΔKHN), and transamelodentinal diffusion were assessed. Enamel surfaces were examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDS) analysis. The data were analyzed using ANOVA, followed by the Student-Newman-Keuls test (p < 0.05).

ΔE*_ab, ΔE₀₀, and ΔWI_D values were comparable among the gels that produced a bleaching effect post-treatment (p < 0.001). The HP/F/TMPnano group exhibited lower mineral loss (SH and ΔKHN), Ra, and H₂O₂ diffusion compared to the 17.5 % HP and 35 % HP groups, which had the highest values (p < 0.001). SEM/EDS analysis revealed surface changes in all bleached groups, though these changes were less pronounced with F/TMPnano.

The 17.5 % HP gel containing F/TMPnano maintains the bleaching effect while reducing enamel demineralization, roughness, H₂O₂ diffusion, and enamel morphological changes.

Low-Concentration H₂O₂ bleaching gel containing F/TMPnano can be used as a novel approach to enhance safety and maintain the performance of aesthetic effects.