INCORPORATION OF NANOHYDROXYAPATITE INTO HYDROGEN PEROXIDE GELS FOR ENAMEL REMINERALISATION DURING BLEACHING

Abstract: Objective: To evaluate the effects of incorporating nanohydroxyapatite (nHA) obtained from eggshell into hydrogen peroxide gels for enamel remineralisation during bleaching. Materials and methods: 10% and 35% hydrogen peroxide (HP) based gels were formulated with different concentrations of hydroxyapatite (HA). Eighty bovine teeth were randomly assigned into eight groups (n = 10): HP 10%, HP 10% + HA 3%, HP 10% + HA 6%, HP 35%, HP 35% + HA 3%, HP 35% + HA 6%, control groups: whiteness HP (FGM) and distilled water. The relative amount of mineral was evaluated by Raman spectroscopy, microhardness values were measured with a Vickers microhardness tester. All evaluations were carried out before and after exposure to the bleaching agents (14 days), as well as one week after bleaching (21 days). Finally, colour was measured using a spectrophotometer at four times. Results: All groups showed a decrease in the relative amount of mineral after being exposed to the bleaching agents; whereas, one week after treatment, a similar recovery to water was observed in the HP 10% and HP 10%+ HA 6% groups (p>0.05). The microhardness values (MPa) did not show statistically significant differences. All experimental groups generated colour changes at all times. At 7 days of treatment, the HP10%+ HA 6% group showed a greater colour change with statistically significant differences. Conclusion: The incorporation of nanohydroxyapatite obtained from eggshell can generate less relative mineral loss, does not modify enamel microhardness and promotes greater colour change during bleaching.