Effect of incorporating calcium polyphosphate submicroparticles into bleaching gels on enamel surface loss after erosive challenge

This in vitro study aimed to evaluate the changes in surface integrity of dental enamel after bleaching using gels with different compositions followed by an erosive challenge. Bovine enamel specimens (4 × 4 × 2 mm; n = 12/group) stored in artificial saliva were treated with bleaching gels containing carbamide peroxide (CP) or hydrogen peroxide (HP) with or without calcium polyphosphate (CaPP) followed by an erosive challenge. In Experiment 1, 10% commercial CP (CPC), CPC + 2% NaF, 10% manipulated CP (CPM), CPM + 2% NaF, 10% CP + 0.5 wt% CaPP, 10% CP + 1.5 wt% CaPP, manipulated gel without CP, or no bleaching were applied for 14 days. In Experiment 2, CP was switched with 35% HP, and all gels were applied for two sessions. Thereafter, all samples were subjected to a 5-day erosive challenge using 1% citric acid (pH 3.5) for 120 s. Enamel surface loss was assessed using contact profilometry and scanning electron microscopy (SEM). Statistical analysis was performed using a generalized linear model (α = 0.05). Compared with that in the CP + 0.5% CaPP and HP + 0.5% CaPP groups, enamel loss was significantly greater in the CPM and CPC groups and HPM and HPC groups in Experiments 1 and 2, respectively. SEM analysis revealed less surface degradation in the groups containing 0.5% CaPP, with greater preservation of the prismatic and interprismatic enamel structure. Both low- and high-concentration bleaching gels containing 0.5% CaPP improved enamel preservation after an erosive challenge compared to that with gels without CaPP. Thus, the addition of CaPP may help minimize enamel damage during bleaching by reducing mineral loss.