This study was undertaken to elucidate the tissue responses to pulsed carbon dioxide laser irradiation with special reference to its tissue ablation property and effect on tissue protection and repair.
Pulsed irradiation was performed on the posterior palatal mucosa and anterior palatal ruga of male Wistar rats, 7-9 weeks of age, with the parameters of 6W, 800μs pulse duration, and pulse repetition rates of 32.47 pps. At 30min, 6, 12, 24, 72 hrs after irradiation, the palatal mucosa was dissected and examined by immunohistochemistry.
In the area irradiated by the pulsed wave, a full thickness of palatal epithelium underwent coagulation necrosis but damages in the subjacent lamina propria were minimal or indiscernible. Re-epithelization took place throughout the wound surface by 24 hrs after irradiation. After 6 to 12 hrs, a strong transient expression of stress protein Hsp70 was observed in the epithelial cells facing the necrotic zone and connective tissue cells in the subjacent lamina propria. The cells expressing anti-macrophage antibody ED1 appeared in the lamina propria adjacent to the necrotic epithelium at 6 and 12 hrs after irradiation, but they were less prominent than in the scalpel incision group. First noted at 6 hrs, an uptake of bromodeoxyuridine, used as a marker for cell proliferation, increased with time and reached a maximum at 24 hrs. The number of labeled cells was significantly larger in the pulsed irradiation group than in the scalpel incision group.
The present results indicate that pulsed irradiation with the parameters in this study is feasible for selective ablation of superficial lesions in oral mucosa and suggest that the irradiation enhances the cell protection system and hence accelerates tissue healing.
