Synthesis and application of calcium cyclotriphosphate in bleaching formulations: Effects on dental enamel properties

OBJECTIVES: This study aimed to synthesize and evaluate the in vitro effects of varying concentrations (0.25%, 0.5%, and 1%) of calcium-substituted sodium trimetaphosphate (CaNaTMP) incorporated into 17.5% and 35% hydrogen peroxide (HP) whitening formulations on enamel color change, microhardness, morphology, surface roughness, mineral content, and transamelodentinal diffusion of HP. MATERIALS AND METHODS: Enamel/dentin discs (N = 288) were allocated into eight groups according to the bleaching gel: (1) 35% HP; (2) 35% HP + 0.25% CaNaTMP; (3) 35% HP + 0.5% CaNaTMP; (4) 35% HP + 1% CaNaTMP; (5) 17.5% HP; (6) 17.5% HP + 0.25% CaNaTMP; (7) 17.5% HP + 0.5% CaNaTMP; and (8) 17.5% HP + 1% CaNaTMP. Gels were applied for 40 min across three weekly sessions. Evaluated parameters included total color change according to CIELab (ΔE), CIEDE2000 equation (ΔE00), whiteness index (ΔWID), surface hardness (SH), surface roughness (Ra), enamel mineral content (gHAp × cm⁻³ × µm), and transamelodentinal of HP. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses were used to assess enamel surface characteristics. Data were analyzed using ANOVA and the Student-Newman-Keuls test (p < 0.05). RESULTS: All bleaching gels caused significant color changes after treatment (p < 0.001), with similar ΔE, ΔE00, and ΔWID values among them. Mineral loss (SH, gHAp × cm⁻³ × µm), Ra, and HP diffusion were highest with the 35% HP gel (p < 0.001) and lowest in groups containing CaNaTMP, particularly at 1% (p < 0.001). SEM/EDX analysis revealed no visible surface alterations in the 17.5% HP group, with prominent amorphous apatite precipitation in the 1% CaTMP-containing group. Incorporating CaNaTMP, particularly at 0.5% and 1%, into the 35% HP gel reduced surface changes. CONCLUSIONS: This study demonstrated that the addition of CaNaTMP to bleaching gels with 17.5% and 35% HP reduces mineral loss, changes in roughness, and surface morphology of enamel, as well as decreasing trans-amelodentinal diffusion of H₂O₂, without compromising the bleaching efficacy. The incorporation of 1% CaNaTMP was particularly more effective in protecting the dental enamel. CLINICAL RELEVANCE: The incorporation of CaNaTMP to 17.5% and 35% HP bleaching gels enhances safety and biocompatibility by reducing enamel damage. The lower HP concentration (17.5%) combined with 1% CaNaTMP provides a safer whitening option, maintaining effectiveness while minimizing adverse enamel changes, aimed at improving patient comfort during treatment.