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

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 (Δ E /Δ E 00 ) 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 Δ E , Δ E 00 , 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