Establishment of treatment that activates oral mesenchymal cells using dental LASER.

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Aim : The purpose of this study was to investigate pulp responses after CO_2 laser irradiation of the cusp of molar teeth using RT-PCR and immunohistochemical methods.Methods : Adult male Sprague-Dawley rats, weighing about 200 g each, were used in this study. A CO_2 laser was used to irradiate the cusp region of the upper first molar with a total energy of 4 J (Density ; 203.84 J/cm^2). The temperature change in the pulp was measured using a super fine sheath thermocouple.Results : The temperature at the pulp side after the CO_2 laser irradiation increased 22.5℃. The expression of both TNFa and IL-1 mRNAs was significantly higher at 6, 12 and 24 hr (but not at 48 hr) after the laser irradiation compared to the control group (p<0.05). Histologically, a slight degeneration of the pulp tissue was observed immediately after the laser irradiation, and HSP-70 positive cells were observed in the pulp horn immediately after the CO_2 laser irradiation. Cells positive for VEGF were seen in the sub-odontoblast layer immediately and 5 days after the laser irradiation. At 5 days after the laser irradiation, the expression of Nestin was recognized in the deeper pulp cells. NFP-positive nerve fibers had disappeared in the pulp horn by 5 days after the laser irradiation.Conclusions : These results suggest that a low energy of laser irradiation such as used in the clinic to the pulp tissue through the dentin induces the inflammatory and pathological cytokine pathways to repair the damaged pulp tissue.