Effect of GaAlAs semiconductor laser irradiation on the permeability of dentin and survival of dental pulp cells

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We investigated the influence of the high-power GaAlAs semiconductor laser on dentin permeability and pulp cells. Sections of 1.0-3.0mm thicknesses were made from a human third molar. Each dentin disk was irradiated with the semiconductor laser and energy that penetrated through the dentin disk was measured by a laser power meter. The laser was applied in CW mode with 0.5-2.0W outputs. We found that the permeability was reduced as the thickness of the dentin increased. In another experiment, a healthy tooth extracted for orthodontic treatment was split to extract the pulp tissue. Irradiated cells were cultured at 37℃ under 5% CO_2, and increases in the number of cells after 24-72 hours were observed. These samples consisted of 25 experimental group samples that were irradiated for 15sec, 30sec, 1min, 3min, or 5min with an irradiation output of 0.5, 1, 2, 5 or 10W. A control group sample was not without irradiated. When the laser was applied to pulp cells, no influence on cell proliferation was noted at 1min, and a decrease in proliferation or death of cells was observed at 3min, with irradiation at 10W by the laser. These results suggest that maintaining appropriate irradiation energy and time based on tooth thickness is necessary when the high-energy semiconductor laser is used.