Influence of bleaching gels formulated with nano-sized sodium trimetaphosphate and fluoride on the physicochemical, mechanical, and morphological properties of dental enamel.

Objectives: To evaluate in vitro the effects of sodium fluoride (F) and nano-sized sodium trimetaphosphate (TMPnano) added to a 35% hydrogen peroxide (H ₂ O ₂ ) bleaching gel on the color alteration, 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: 35% H ₂ O ₂ (HP); 35% H ₂ O ₂  + 0.1% F (HP/F); 35% H ₂ O ₂  + 1% TMPnano (HP/TMPnano); 35% H ₂ O ₂  + 0.1% F + 1% TMPnano (HP/F/TMPnano) and 35% H ₂ O ₂  + 2% calcium gluconate (HP/Ca). The gels were applied 3 times by 40 min; once each 7-day. The Commission Internationale de l'Eclairage (CIE) L*a*b* total color alteration (ΔE), color alteration by CIEDE2000 (ΔE ₀₀ ), whitening index (ΔWI _D ), surface (SH) and cross-sectional hardness (ΔKHN), surface roughness (Ra), and transamelodentinal diffusion were determined. Enamel surfaces were evaluated by Scanning Electron Microscopy (SEM) and X-ray Dispersive Energy (EDX). Data were submitted to ANOVA, followed by the Student-Newman-Keuls test (p <0.05).
Results: ΔE, ΔE ₀₀ , and ΔWID were similar among the gels that promoted a bleaching effect after treatment (p <0.001). Mineral loss (SH and ΔKHN), Ra, and H ₂ O ₂ diffusion were lower for HP/F/TMPnano; the HP and HP/Ca groups presented the highest values (p <0.001). For SEM/EDX, surface changes were observed in all bleached groups, but less intense with TMPnano.
Conclusions: Gels containing F/TMPnano do not interfere with the bleaching effect and reduce enamel demineralization, roughness, H ₂ O ₂ diffusion, and morphological changes.
Clinical Relevance: Whitening gels containing F/TMPnano can be used as a new strategy to increase safety and maintain clinical performance.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The last author holds a patent for a product used in the study, by the National Institute of Industrial Property – INPI/SP, issued on November 05, 2019, under number BR 102,013,006,761–0.
(Copyright © 2023. Published by Elsevier Ltd.)