[Experimental studies in the healing process of the rats tongue after Nd:YAG contact laser irradiation. Scanning electron microscopic observation].

The Nd:YAG laser is useful in clinical oral surgery because of its superior hemostatic and coagulating effects. The purpose of this study was to examine the healing process of the tongue wounds caused by the Nd:YAG contact laser. A scanning electron microscope (SEM) was used, focusing mainly on the papillae filiformes of the tongue, and the results were compared with the pathological findings. The laser's effect on the microcirculatory network and the healing process were observed using the injection replica scanning electron microscope method. One hundred and eighty nine male Wistar rats were used in the experiment. Irradiation condition were 3, 6, 9 and 12-W for 1.0 second. The rats were sacrificed immediately after irradiation and on the 1st, 4th, 7th, 10th, 14th, 21st, 28th and 56th days after irradiation. The results were as follows. Pathological observations; Immediately after irradiation, the 3-W wound was observed below the lamina propria. The 6-W and 9-W wounds were observed from the upper musculi transversus linguae to the near center. The 12-W wound was observed to the center of the musculi transversus linguae. SEM observations; In the case of the 3-W wound, on the 7th day, normal epithelization was largely complete and there was a mucosal bulge which appeared to be regenerating papillae filiformes at the edge of the wound. On the 28th day, regenerated papillae filiformes were observed over the entire surface of the wound. The similar healing process was observed for the 6, 9 and 12-W wounds. However, in the cases of the 6-W and 9-W wounds the regenerated papillae filiformes were morphologically different from the original ones. In the case of the 12-W wound, on the 56th day regenerated papillae filiformes were observed around the edge of the wound but not in the center. Injection replica SEM observations; Concerning the effect of contact laser irradiation (6-W) on the tongue's microcirculatory network, the blood vessels at the edge of the wound were cut straight off, which suggested that they had been cauterized. Observations of the network during the healing of the wound showed that capillary loops had been restored and were related to the papillae filiformes.