Effects of different concentrations of carbamide peroxide on enamel structure

Objectives: To investigate the effects of three carbamide peroxide bleaching agents in different concentrations (10%, 15%, and 20%) on the surface morphology and chemical composition of enamel. Methods: Enamel specimens were randomly divided into four groups. Three different concentrations of carbamide peroxide (10%, 15%, and 20%) were tested in the study. All bleaching materials were applied to the specimens per the manufacturer's instruction for 15 days. The fourth group served as the control and was kept in distilled water during the test period. Surface morphology was examined using scanning electron microscopy and chemical composition of enamel was analyzed by infrared spectroscopy, X-ray diffraction and Raman spectroscopy. Results: Scanning electron microscopy showed that all three different concentrations of carbamide peroxide changed the surface morphology of enamel. Infrared spectroscopy, X-ray diffraction and Raman spectroscopy analyses showed there were no significant difference in inorganic chemical composition between the experimental groups and the control. The fluorescence spectra recorded by Raman spectroscopy showed fluorescence of the experimental groups decreased dramatically compared with the control. Conclusions: All three different concentrations of carbamide peroxide do affect the organic part of enamel but have little effect on the inorganic.