Maintenance of enamel properties after bleaching with high-concentrated hydrogen-peroxide gel containing calcium polyphosphate sub-microparticles

Abstract

Objective: To assessed the physical and chemical properties of human-enamel after treatment with an experimental bleaching gel containing 35%-hydrogen peroxide (HP) and calcium polyphosphate sub-microparticles (CaPP).

Materials and methods: Enamel/dentin specimens (4 × 4 × 3 mm) were obtained (n = 120) and allocated to different groups: control (saliva only); experimental (HP35%); commercial (whiteness-HP-Maxx); CaPP0.5% (HP35% + CaPP0.5wt%); CaPP1.5% (HP35% + CaPP1.5wt%). Three sessions were performed. The specimens' color was assessed using a spectrophotometer and the color (ΔE/ΔE₀₀) and bleaching index (ΔWID) determined. The surface roughness and microhardness were assessed with a roughness tester and Knoop indenter. Raman spectroscopy was performed to obtain the ratios between the areas under the 431, 580, and 1070 cm^-1 and the 960 cm^-1 bands (430:960, 580:960, 1070:960). Kruskal-Wallis and Dunn compared the color, Ra, and SMH data. The Raman data was analyzed with Kruskal-Wallis and Dunn (α = 5%).

Results: The ΔE, ΔE₀₀, and ΔWID were similar among the bleached groups (p > 0.05). The roughness was not different between the groups (p > 0.05). After the 3^rd session, CaPP0.5% had higher microhardness than the experimental (p < 0.05). The 1070:960 was higher in the experimental than in the CaPP1.5% and control (p < 0.05).

Conclusions: In human enamel, CaPP did not alter the bleaching effectiveness or roughness, and additionally, CaPP-containing gels increased the microhardness and preserved the mineral content when compared to the experimental without CaPP.

Clinical relevance: Experimental bleaching gels containing calcium polyphosphate sub-microparticles as a mineral source reduce the mineral content alteration and superficial microhardness reduction, known potential side effects of the in-office bleaching treatments.

Keywords: Calcium polyphosphate; Dental enamel; Polyphosphates; Raman spectroscopy; Tooth bleaching.