Abstract
This study proposes a method of measuring the dynamic force induced by laser irradiation on the human tooth. The dynamic load induced in a specimen by using elastic wave propagation in a long aluminum-alloy bar was measured. The laser-induced stress intensity was evaluated from the dynamic strain which was measured by semiconductor strain gauges attached to the long bar. In addition, the process of laser irradiation to the hard tissue surface was observed with an ultrahigh-speed video camera. Carbon powder and titanium dioxide powder were applied to the dentin surface so as to effectively absorb the laser beam. The results showed that the hard tissue surface was flashed during the laser irradiation, and the melted tissues continued to scatter in the direction perpendicular to the tissue surface in a mushroom-like wave. The measured dynamic stress induced on the surface increased with the increase of laser energy and was closely related to the prepared cavity on the surface. The titanium dioxide powder more effectively induced stress than the carbon powder. The induced dynamic stress for eliminating a unit volume of hard tissue was 0.03 Pa/mm3.
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