Effect of bleaching teeth with hydrogen peroxide in the morphology, hydrophilicity, mechanical and tribological properties of enamel

The oral aesthetic medicine has contributed increasingly to correct aesthetic defects in order to respond to the standards of beauty imposed by society. A smile with white teeth is included in these standards. However, due to several factors, such as diet, age and certain vices, the natural color of teeth tends to change. The bleaching of teeth pretends to restore the original color of the teeth and consists in application of oxidizing agents, including hydrogen peroxide, on their surface. Although these products improve considerably the color of teeth, their effect on other properties of enamel is not yet fully understood. This work aimed to study the impact of peroxide concentration used for tooth whitening in hydrophilicity, roughness, morphology, mechanical and tribological properties of human enamel. With this purpose, human teeth were submitted to bleaching sessions with 6, 15 and 35% hydrogen peroxide, activated with UV radiation, to achieve maximum bleaching level B1. The enamel roughness and morphology was studied by AFM and SEM, the hardness using a microhardness tester, the hydrophilicity by the captive bubble method (as far as we know, never used to characterize teeth), and the tribological behavior using a nanotribometer. The results show that, although the three solutions are able to improve the teeth color, they alter the properties of the enamel, inducing morphological changes, increase its roughness and wettability and decrease the hardness and wear resistance. It was found that the 15% hydrogen peroxide was the solution that less damaged enamel.