Effects of He-Ne Laser Photobiomodulation on Cortical Bone Regeneration in a Rat Femoral Defect Model

Abstract Photobiomodulation (PBM) therapy using low-level lasers has been reported to promote wound healing and bone regeneration. However, fundamental studies on its effects in cortical bone healing remain limited. To investigate the effects of helium-neon (He-Ne) laser-induced PBM on cortical bone regeneration in a rat femoral defect model. Cylindrical cortical bone defects were surgically created in both femora of rats. One side received He-Ne laser irradiation (632.8 nm, 25 mW, 5 min per session, 5 consecutive days), while the contralateral side served as the control. Bone healing was evaluated at 7 and 14 days postoperatively using micro-computed tomography (μ-CT) and histological analysis of non-decalcified sections. At day 7, μ-CT analysis showed no significant differences between the groups. However, histological evaluation revealed immature collagen-rich bone in the control group, whereas the laser-irradiated group exhibited more advanced mineralization. By day 14, the laser-irradiated group demonstrated significantly greater bone surface area and trabecular number, along with reduced trabecular thickness and spacing, indicating the formation of a finer and more complex trabecular structure. PBM with He-Ne laser may enhance cortical bone regeneration by promoting microarchitectural remodeling of newly formed bone. These findings support its potential to accelerate bone healing in critical-size defects.