This study was undertaken to provide a light microscopic and ultrastructural basis to compare the early healing events at Er:YAG and CO2-lased bone tissue. Twenty-four male Wistar rats were used in this study. After anesthetizing, the calvarial bone was irradiated by Er:YAG laser in a contact mode at an energy output of 100 mJ/pulse and 10 pps with water coolant and by CO2 laser with an energy output of 4 W. The rats were then sacrificed at 10 min, 6 and 24 h and 3, 7 and 14 days after irradiation. The histopathological study of healing following Er:YAG laser irradiation suggested that this mode of treatment had a beneficial effect on initial bony wound healing. It was found that proliferation of fibroblasts and osteoblasts were more prominent in this group and, thus, were revascularization and the formation of osteoid tissue. On the contrary, large amounts of necrotic tissue, char and carbonized tissue with polymorphonuclear leukocytes (PMNs) were the major histological features in the CO2 laser specimens. We conclude that Er:YAG laser irradiation did not adversely affect the bone healing process and would be applicable for bone surgery. (C) 2003 Elsevier Science B.V. All rights reserved.
