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

The tooth whitening process is intended to restore the original color of teeth. It consists of the application of oxidizing agents, including hydrogen peroxide. Although these products considerably improve the color of teeth, their effects on other properties of enamel are not fully understood. This work aimed to study the effects of hydrogen peroxide concentration on hydrophilicity, roughness, morphology, and mechanical and tribological properties of human tooth enamel. Human teeth were subjected to bleaching sessions with 6%, 15%, and 35% hydrogen peroxide to achieve a similar level of whitening. The enamel roughness and morphology were characterized by atomic force microscopy and scanning electron microscopy. Vickers microindentation hardness data were obtained. The hydrophilicity was determined using the captive bubble method. Reciprocating, ball-on-flat friction, and wear tests were conducted in artificial saliva using zirconia as the ball and polished enamel as the flat specimens. Although all three test solutions improved tooth color, they also changed the properties of the enamel. Morphological and roughness changes were observed, and there was a decrease in hardness and wear resistance. The wettability was nearly unaffected. It was found that the 15% hydrogen peroxide solution damaged the enamel the least. It was concluded that there is an ideal concentration of hydrogen peroxide for whitening treatments. [Display omitted] •H2O2 bleaching increases the enamel surface roughness and decreases its hardness.•The enamel hydrophilicity is slightly affected by H2O2 treatment.•A dramatic increase in friction and wear coefficients is observed after treatment.•A 15% H2O2 solution produces minor changes in enamel properties compared to 6% and 35% solutions.•The results suggest the existence of an ideal concentration of H2O2 for bleaching.