Purpose: The purpose of this study was to investigate the morphological changes of rat palatal mucosa after CO2 laser irradiation. Materials and Methods: The laser ablations were made with the CO2 laser in continuous wave mode, 1 W, for 5 s. For light microscopic observations, animals were killed immediately, 0.5, 1 to 5 and 7 days after irradiation. The sections were stained immunohistochemically with primary antibodies: laminin, S100, polyclonal-keratin, HMB45 and CK20. For electron microscopic observation, tissues were fixed immediately and 12 h after irradiation. Results: Immediately after irradiation, degeneration of the superficial layer of the epithelium was observed; however, the cells of the basal and para-basal layers were well preserved. Twelve hours after irradiation, the epithelium had degenerated; however, a laminin-positive reaction was still recognized at the basal membrane. The electron microscopy showed that, although the cell membranes had become unclear, desmosome-like structures were preserved. One day after the laser irradiation, the epithelium had separated from underneath the lamina propria. At 2 days after the irradiation, the irradiated areas were covered by fibrin materials without any visible damage of the connective tissue. At 7 days after the irradiation, the epithelium had regenerated completely without any cells positive for S-100, HMB45 or CK20. Conclusion: These results suggest that the CO2 laser affected binding proteins of the basal membrane without destroying the underlying connective tissue.
Keywords: CO2 laser, oral mucosa, immunohistochemistry, electron microscopy