Study on Measurement of Dynamic Stress Induced by Nd:YAG Laser Beam

In dental treatment, a laser beam has been used for various surgical treatments of hard and soft tissues. Recently, there has been considerable interest in the bactericidal effect induced by laser beam irradiation. This paper deals with the measurement of dynamic stress induced in extracted human enamel by irradiation with Nd:YAG laser beam. The laser beam can be delivered to the specimen through a quartz optical fiber. The dynamic load induced in the specimen by using elastic wave propagation in the cylindrical long bar made of aluminum alloy was measured. The human enamel was grinded with the grain size of 26 m, and carbon powder and titanium dioxide powder were applied to the surface so as to absorb the laser beam effectively. The laser induced stress intensity was evaluated from the dynamic strain measured by small semiconductor strain gauges. The result showed that the induced dynamic stress increased with the increase of laser energy in each absorbent. The induced dynamic stresses with TiO 2 powder were superior to that with carbon powder. The induced dynamic stress was related to the volume of prepared cavity. The induced stress for the removal of the unit volume of human enamel was 0.03 Pa/mm 3 .