Effects Of Hydrogen Peroxide On Human Enamel Structure

Objectives: The aim of this study was to describe the effects of hydrogen peroxide on enamel structure. Methods: 10-20-30 % hydrogen peroxide solutions were used for treatment of human enamel samples. Thirty samples made from human tooth crown. Enamel structure was investigated by atomic force microscopy (AFM), and FT-IR spectroscopy. The total treatment time was 120 minutes. Infrared spectra and AFM scan was taken before treatment, thus each specimen served its own negative control. Further spectra and scans were taken after 30, 60 and 120 minutes. After the 2-hour treatment samples were stored in isotonic salt solutions for two weeks. At the end of the 2-week incubation period, another set of infrared spectra and surface scan were taken to test spontaneous reversibility in enamel structure. Results: AFM images showed shallow grooves with depth and width varied between 28-84 nm and 100-250 nm, respectively. Treatment with 20% and 30% solutions further increased the width and depth of the grooves. There was no spontaneous reversibility detected by AFM after the two-week storage in isotonic salt solution. Enamel specimens showed a characteristic infrared spectrum with two distinct peaks, representing the hydroxiapatite structure ν1 at 996 cm-1 and ν2 between 1410 and 1460 cm-1 wavelength before hydrogen peroxide treatment. Alterations in the IR spectra were found after hydrogen peroxide treatment in all cases (i.e. peroxide concentration and treatment time). Both ν1 and ν2 bands became distorted after treatment. The ν2 peak was missing after the 30% hydrogen peroxide treatment. Neither the ν1, nor the ν2 bands showed spontaneous alterations after the two-week period. Conclusion: The alterations on enamel surface and inner structure were directly proportional to the treatment time and the hydrogen peroxide concentration. The work/publication is supported by the TÁMOP 4.2.1/B-09/1/KONV-2010-0007 project. The project is co-financed by the European Union,European Social Fund.