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

Objectives: To evaluate in vitro the effects of nano-sized sodium trimetaphosphate (TMPnano) and sodium fluoride (F) added to a 17.5 % hydrogen peroxide (H ₂ O ₂ ) bleaching gel on the color change, enamel mechanical and morphological properties, and H ₂ O ₂ transamelodentinal diffusion.
Materials and Methods: Bovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 17.5 % H ₂ O ₂ (17.5 % HP); 17.5 % H ₂ O ₂ + 0.1 % F (HP/F); 17.5 % H ₂ O ₂ + 1 % TMPnano (HP/TMPnano); 17.5 % H ₂ O ₂ + 0.1 % F + 1 % TMPnano (HP/F/TMPnano) and 35 % H ₂ O ₂ (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 (ΔE ₀₀ ), 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).
Results: ΔE* _ab , ΔE ₀₀ , 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 H ₂ O ₂ 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.
Conclusions: The 17.5 % HP gel containing F/TMPnano maintains the bleaching effect while reducing enamel demineralization, roughness, H ₂ O ₂ diffusion, and enamel morphological changes.
Clinical Relevance: Low-Concentration H ₂ O ₂ bleaching gel containing F/TMPnano can be used as a novel approach to enhance safety and maintain the performance of aesthetic effects.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper; except for the last author, who holds a patent for a product used in the study, issued on November 5, 2019, under BR 102013006761-0.
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