Total sodium replacement by calcium in trimetaphosphate and its incorporation into dental whitening gels: A novel strategy for in-office treatment

Abstract

Objectives: The aim of this study was to synthesize a cyclophosphate with total sodium replacement (CaTMP) and to evaluate, in vitro, its incorporation into hydrogen peroxide (HP) whitening gels.

Materials and methods: CaTMP was synthesized through column chromatography using ion-exchange resin and calcium hydroxide solution. Bovine enamel/dentin discs (n = 150) were divided into five groups: 1) negative control (no treatment), 2) 35 % HP whitening gel (positive control), 3) 35 % HP + 1 % CaTMP, 4) 17.5 % HP, and 5) 17.5 % HP + 1 % CaTMP. Whitening gels were applied weekly for three 40-minute sessions. Color change was measured using ΔE, ΔWI_D, and ΔE₀₀. Transamelodentinal HP diffusion was determined, as well the mineral content of dental substrates by μ-CT (g_HAp × cm^-3 × µm). Data were analyzed with ANOVA and Student-Newman-Keuls test (p < 0.05).

Results: All whitening gels caused significant color changes (p < 0.001), with no differences between groups in ΔE, ΔE₀₀, and ΔWI_D (p > 0.05). The highest transamelodentinal HP diffusion occurred in the 35 % HP group (p < 0.001), but adding 1 % CaTMP reduced this diffusion in both HP concentrations (p < 0.05), with a greater reduction in the 17.5 % HP gel. Conventional gels (17.5 % and 35 % HP) caused greater mineral loss (g_HAp × cm^-3 × µm), while CaTMP protected against these changes.

Conclusions: Incorporating 1 % CaTMP into whitening gels (17.5 % and 35 % HP) significantly reduced HP diffusion and preserved the mineral content of enamel and dentin, while providing whitening results similar to conventional gels.

Clinical relevance: CaTMP may act as a protective agent against peroxide-induced oxidative damage in dental tissues. While these findings are based on in vitro data, they support a promising direction for future translational research aimed at enhancing the safety and effectiveness of in-office whitening procedures.

Keywords: Calcium; Enamel; Hydrogen peroxide; Phosphates; Tooth whitening.