Low-energy laser stimulates tooth movement velocity via expression of RANK and RANKL.
OBJECTIVE
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. The receptor activator of the nuclear factor-kB (RANK) / RANK ligand (RANKL) / osteoprotegerin (OPG) system is essential and sufficient for osteoclastogenesis. The present study was designed to examine the effects of low-energy laser irradiation on expressions of RANK, RANKL, and OPG during experimental tooth movement.


METHODS
To induce experimental tooth movement in rats, 10 g of orthodontic force was applied to the molars. Next, 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 RANK, RANKL, and OPG was performed. Real time PCR was also performed to elucidate the expression of RANK in irradiated rat osteoclast precursor cells in vitro.


RESULTS
In the irradiation group, the amount of tooth movement was significantly greater than in the non-irradiation group by the end of the experimental period. Cells that showed positive immunoreactions to the primary antibodies of RANKL and RANK were significantly increased in the irradiation group on day 2 and 3, compared with the non-irradiation group. In contrast, the expression of OPG was not changed. Further, RANK expression in osteoclast precursor cells was detected at an early stage (day 2 and 3) in the irradiation group.


CONCLUSIONS
These findings suggest that low-energy laser irradiation stimulates the velocity of tooth movement via induction of RANK and RANKL.
Fujita
S
S
Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan. fujita.shouji@nihon-u.ac.jp
Yamaguchi
M
M
Utsunomiya
T
T
Yamamoto
H
H
Kasai
K
K
D000818:Animals; D016723:Bone Remodeling / Q000502:physiology / Q000528:radiation effects*; D003799:Dental Stress Analysis; D007150:Immunohistochemistry; D054023:Lasers, Semiconductor; D008297:Male; D010010:Osteoclasts / Q000528:radiation effects*; D053244:Osteoprotegerin / Q000096:biosynthesis*; D053245:RANK Ligand / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014087:Tooth Movement Techniques
D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B