SYNOPSIS
Previously, the authors have reported the acceleration of tooth movement and osteoclastogenesis on the pressure site in an experimental tooth movement model by low-energy laser irradiation (LELI). Osteopontin (OPN) is an essential and suf-ficient for osteoclastogenesis. However, the effect of LELI on osteogenesis on the tension site is not known clearly. Therefore, the present study was designed to examine the effects of LELI on the expression of OPN during experimental tooth movement. To induce experimental tooth movement in rats, 10 g force was applied to the upper right first molar with a Nickel titanium closed-coil spring. Next, a gal-lium-aluminum-arsenide (Ga-Al-As) diode laser was used to irradiate the area around the moved tooth, and the amount of tooth movement was measured for 21 days. Histopathological examination was also performed. Furthermore, the effect of LELI on OPN release from stretched human periodontal ligament (hPDL) cells was evaluated by Enzyme-linked immunosorbent assay (ELISA) in vitro. The amount of tooth movement in the LELI group was significantly greater than in the non-irradiation group by the end of the experimental period. Cells positively stained with OPN were found to be significantly increased in the LELI group on days 3 as compared with the non-irradiation group. Furthermore, the OPN re-leases from stretched hPDL cells were significantly higher concentration in the LELI group than in the non-irradiation group in vitro.
These findings suggest that LELI induces the expression of OPN in tension side during orthodontic tooth movement.

Key words: Low-energy laser irradiation, osteopontin, orthodontic tooth movement