The Effect of Beam Direction on Absorption and Transmission of Ultraviolet to Infrared Wavelength Regions in Three Different Dentin Thicknesses

Lasers and optics have been used extensively in dental procedures in recent years, and realizing the optical properties of the tooth is also an essential in its successful applications. The aim of this study was to compare the absorption and transmission of applied wavelengths in the range of 190–1100 nm at different dentin thicknesses and the effect of changing the direction of radiation emission on the dentin tubules.

There were fifteen dentin specimens with thicknesses of 300, 600, and 1000 mm, five specimens for each thickness, prepared through a transverse section of the coronal dentin over the pulpal roof area of human molars. Considering the coronal-apical and apical-coronal directions, we measured the absorption and transmission of parallel light rays perpendicular to the dentin samples in different thicknesses and two directions with a Cecil CE 7400 UV/Vis spectrometer. Data analysis was performed using SPSS software version 19. P value < 0.05 was considered significant.

The absorption rate of the ultraviolet wavelength range was significantly higher than that of visible and infrared light irradiation from both directions at three thicknesses (P < 0.001). The radiation shift direction had no significant differences in the absorption and transmission of wavelengths of ultraviolet, visible, and infrared light in any of the three thicknesses (P > 0.05).

Accordingly, attenuation or transmission losses of light in the ultraviolet to infrared range clearly depend on the wavelength of light and the optical properties of dental dentin, and the thickness of the dentin used in this study has a little effect.