Penetration of IR laser radiation in human teeth: angular distribution of light and coefficients of absorption and scattering

Abstract

We have developed techniques and practical set-ups and have studied comparatively the propagation of a traditional 1.06 μm laser emission and a non-familiar 1.36 μm line of the widespread Nd:YAG laser in human dentin (pure) samples and in combined enamel-dentin samples. The wavelength 1.36 μm can be obtained with high energy output using some non-complicated modification of Nd:YAG laser, as it is further shown in this work. This wavelength is of potential interest for application in dentistry due to its known higher absorption in comparison with a 1.06 μm line in human soft tissues. Thus, it is possible that it would also be highly absorbed in hard dental tissues. As a result of our investigation on human pure dentin samples and combined enamel-dentin samples, we have obtained the following parameter estimates: 1) reflectivity of these two tissue substances; 2) the full coefficient of the extinction and angular distribution of the intensity (in the cross-sections) of the penetrated light in the examined dental substances; 3) as a main point, combining the optical and calorimetric techniques, we have obtained separately the absorbed and the diffused part of the light, and have calculated separately the coefficients of absorption and scattering in the dentin. The study is based on in vitro examination of fresh teeth samples from participants from Bulgaria, Sofia region.