Low-energy laser irradiation stimulates the tooth movement velocity via expression of M-CSF and c-fms

Recent studies have demonstrated that low-energy laser irradiation stimulates bone formation in vitro and in vivo. However, very little is known about the effects of laser irradiation on osteoclastogenesis. Macrophage colony-stimulating factor (M-CSF) is essential and sufficient for osteoclastogenesis. The present study was designed to examine the effects of low-energy laser irradiation on expressions of M-CSF and c-fms during experimental tooth movement. A total of 10 g of orthodontic force was applied to rat molars to cause experimental tooth movement. A Ga-Al-As diode laser was used to irradiate the area around the moved tooth and the amount of tooth movement was measured for 7 days. Immunohistochemical staining with M-CSF and c-fms was performed. RT-PCR was also performed to elucidate the expression of c-fms from irradiated rat osteoclast precursor cells. In the irradiation group, the amount of tooth movement was significantly greater than that of the non-irradiation group at the end of the experiment. Cells positively stained with M-CSF and c-fms were found to be significantly increased in the irradiation group on days 2 and 3 as compared with the non-irradiation group. Further, c-fms expression in osteoclast precursor cells was detected at an early stage (days 2 and 3) in the irradiation group. These findings suggest that low-energy laser irradiation stimulates the velocity of tooth movement via the expressions of M-CSF and c-fms.