The objective of this in vitro study was to establish the hydrogen peroxide (H2O2) and oxygen (O2) kinetics in enamel surface following a tooth bleaching procedure, using confocal micro Raman spectroscopic technique.
Materials and Methods:
3 anterior sound teeth were used. Cuts were made in order to obtain a total of 9, 2x2 mm buccal enamel samples. A bleaching product containing 40% hydrogen peroxide (Opalescence Boost) was applied to these samples, for 1 hour, rinsed with water and dried immediately before measurements. Samples were measured with confocal micro Raman spectrometer equipped with a laser diode source operating at a wavelength of 532 nm. The incident laser power applied to the sample was 8 mW. The spectral ranges investigated were 800 cm-1 to 1700 cm-1 using a pinhole of 500 µm, a 100 µm slit and a 1800 g/mm grating. Pictures have been taken with a BX41 Olympus microscope using x10 and x100 magnification and equipped with a Ueye 1640 camera. Integrated intensities have been calculated for the peak assigned to O2, phosphate (PO4) and H2O2, then the ratios O2/PO4 and H2O2/PO4 have been calculated and plotted with time to show the kinetics decrease of O2 and H2O2 after the bleaching process. Calculation for time are presented as Mean ± SEM
Results:
Spectra obtained showed a progressive decrease in the peak assigned to H2O2 (875 cm-1) while O2 (1552 cm-1) showed a slight increase in the first minutes and then a progressive decrease. The average time needed to achieve 1% of initial amount of H2O2 and O2are respectively 14.7 ± 2.1 hours and 96.5 ± 18.5 hours
Conclusion:
Hydrogen Peroxide has a faster decrease in enamel surface when compared to oxygen. Oxygen continued to be generated in enamel surface for a few time after the removal of bleaching gel.