Effects of hydroxyapatite in combination with hydrogen peroxide on enamel

Objective: The purpose of the study was to evaluate the effects of hydroxyapatite (HA) in combination with hydrogen peroxide (HP) on color, microhardness and morphology of human tooth enamel. Methods: Human enamel blocks were randomly divided into four groups with 12 specimens each: group A (HA and HP), group B (HP), group C (HA and DW) and group D (DW). Baseline and final color measurements and microhardness test were carried out before and after bleaching experiments. Two specimens from each group were selected for morphological investigation after final tests. Results: The DE of group A and B were significantly higher than that of group C (p=0.000 and p=0.000) and D (p=0.000 and p=0.000). The percentage microhardness loss of group A was significantly lower than that of group B (p=0.047), but significantly higher than that of group C (p=0.000) and D (p=0.000). The obvious variation of morphology was only observed on enamel surfaces in group B. Conclusions: HA in combination with HP was effective in tooth whitening and could inhibit enamel demineralization and reduce microhardness loss.