Influence of Er:YAG laser ablation on cavity surface and cavity shape

摘要

Abstract: The cavity surface and shape after Er:YAG laser ablation at different energies, number of pulses and at a different repetition rate were observed. Longitudinal sections of extracted human incisors and transverse sections of ivory tusk were cut and polished to flat and glazed surfaces. The samples thickness was from 3 to 5 mm. The Er:YAG laser was operating in a free-running (long pulse) mode. The laser radiation was focused onto the tooth surface by CaF$-2$/ lens (f $EQ 55 mm). During the experiment, the teeth were steady and the radiation was delivered by a special mechanical arm fixed in a special holder; fine water mist was also used (water-mJ/min, a pressure of two atm, air-pressure three atm). The shapes of the prepared cavities were studied either by using a varying laser energies (from 70 mJ to 500 mJ) for a constant number of pulses, or a varying number of pulses (from one to thirty) for constant laser energy. The repetition rate was changed from 1 to 2 Hz. For evaluating the surfaces, shapes, and profiles, scanning electron microscopy and photographs from a light microscope were used. The results were analyzed both quantitatively and qualitatively. It is seen that there is no linear relation between the radiation pulse energy and the size of the prepared holes. With increasing the incident energy the cavity depth growth is limited. There exists some saturation not only in the enamel and dentin but especially in the homogeneous ivory.!10