Histological and TEM Examination of Early Stages of Bone Healing after Er:YAG Laser Irradiation

Objective: The aim of this study was to analyze the early healing process of bone tissue irradiated by Er:YAG laser and compare it with that treated by mechanical drilling and CO₂ laser. Background Data: Er:YAG laser has a great potential for cutting hard tissues as it is capable of ablation with less thermal damage. Methods: Twenty-four male Wistar rats were used for this study. The calvarial bone of rats was exposed and straight grooves were prepared by Er:YAG laser, mechanical bur and continuous wave CO₂ laser. Four rats each were sacrificed at six time points: 10 min, 6 and 24 h and 3, 7, and 14 days post-surgery. Sections were prepared for light and transmission electron microscopic (TEM) observations. Results: Compared to mechanical bur and CO₂ groups, the inflammatory cell infiltration adjacent to the irradiated bone surface, fibroblastic reaction, and revascularization were more pronounced in the Er:YAG laser-irradiated tissues. A cell-rich granulation tissue with fibroblasts and osteoblasts was predominant in 7-day specimens of Er:YAG laser group. Histopathological analysis of 14-day specimens in the Er:YAG group also revealed significantly greater new bone formation, compared with the mechanical bur and CO₂ laser groups. Conclusions: Initial bone healing following Er:YAG laser irradiation occurred faster than that after mechanical bur and CO₂ laser. Er:YAG laser treatment may be advantageous for wound healing of bone tissue, presumably by providing a favorable surface for cell attachment.