Evaluation of bleaching efficacy, microhardness, and trans-amelodentinal diffusion of a novel bleaching agent for an in-office technique containing hexametaphosphate and fluoride.

OBJECTIVE

This study evaluated in vitro the effects of calcium gluconate (CaGlu), sodium fluoride (NaF), sodium hexametaphosphate (HMP), and NaF/TMP added to a 35% hydrogen peroxide (HO) bleaching gel on the color change, enamel hardness, and trans-amelodentinal diffusion.

MATERIALS AND METHODS

Enamel discs/bovine dentin (n = 150) were divided according to the bleaching gel: 35% HO (HO); 35% HO + 0.1% NaF (HO/NaF); 35% HO + 1% HMP (HO/HMP); 35% HO + 0.1% NaF + 1% HMP (HO/NaF/HMP), and 35% HO + 2% CaGlu (HO/Caglu). The bleaching gels were applied three times (40 min/session) at 7-day intervals between each application. Then, color alteration (ΔE), whitening index (ΔWI), percentage of surface hardness loss (% SH), cross-sectional hardness (ΔKHN), and trans-amelodentinal diffusion were determined. Data were submitted for analysis of variance (ANOVA), followed by the Student-Newman-Keuls test (p < 0.05).

RESULTS

All bleaching gels showed significant color changes after treatment (p < 0.001). ΔE and ΔWI were similar among the evaluated gels. Mineral loss (% SH and ΔKHN) and trans-amelodentinal diffusion of hydrogen peroxide were lower for HO/NaF/HMP; the HO/CaGlu group presented the highest values about the other groups (p < 0.001).

CONCLUSION

It is possible to conclude that the addition of NaF/HMP to the in-office bleaching agent did not interfere with the bleaching efficacy and reduced enamel demineralization and HO diffusion.

CLINICAL SIGNIFICANCE

The association of NaF/HMP to the bleaching gel can be used as a novel approach for minimizing the adverse effects of HO by-products and with similar clinical efficacy.