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

Abstract

Abstract Objectives To evaluate in vitro the effects of sodium fluoride (F) and nano-sized sodium trimetaphosphate (TMPnano) added to a 35% hydrogen peroxide (H2O2) bleaching gel on the color alteration, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion. Materials and Methods Bovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 35% H2O2 (HP); 35% H2O2 + 0.1% F (HP/F); 35% H2O2 + 1% TMPnano (HP/TMPnano); 35% H2O2 + 0.1% F + 1% TMPnano (HP/F/TMPnano) and 35% H2O2 + 2% calcium gluconate (HP/Ca). The gels were applied 3 times by 40 min; once each 7-day. Color alteration (ΔE and ΔE00), whitening index (ΔWID), 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, ΔE00, and ΔWID were similar among the evaluated gels that produced a bleaching effect after enamel pigmentation (p < 0.001). Mineral loss (SH and ΔKHN), Ra, and H2O2 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 reduced enamel demineralization, roughness, H2O2 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.