Comparative Study of 660 and 830 nm Photobiomodulation in Promoting Orthodontic Tooth Movement

Photobiomodulation (PBM) can usefully promote wound healing and relieve pain via its biological effects, with a wide range of applications in clinical medicine. The aim of the present study was to investigate the effect of 660 and 830 nm PBM on orthodontic tooth movement. PBM is based on the biological effects of diode laser irradiation on tissues, promoting cell proliferation and activity. An orthodontic force was applied to the upper right first molars exposed to a 660 and 830 nm PBM (LHH-500I; Beijing Long Hui Heng Medical Science and Technology Development Corporation) on days 0, 1, 2, 3, 4, 5, and 7 for 50 sec with power density of 0.1 W/cm² (a beam area of 0.5 cm², radiate power of 0.05 W), energy density of 5 J/cm² within 14 days, and a control group with no laser irradiation. Tooth movement was analyzed using a stereomicroscope, the number of osteoclasts determined by tartrate-resistant acid phosphatase (TRAP), and the expression of bone remodeling factors evaluated by immunohistochemistry. The expression of IL-1β, RANKL, and OPG was significantly stimulated in the 660 and 830 nm groups. The expression of RANKL was significantly higher in the 660 nm group than in the 830 nm group on days 5 and 7; however, there was no significant difference in the expression of OPG and IL-1β between the 660 and 830 nm groups on days 1, 2, 3, 4, 5, 7, and 14. On days 3 and 5, the number of osteoclasts in the 660 nm group was higher than that in the 830 nm group, and the difference was statistically significant. Tooth movement over 14 days was significantly higher in the 660 and 830 nm groups than in the control group, and there was no significant difference between the 660 and 830 nm groups finally. Both 660 and 830 nm can accelerate the orthodontic tooth movement and promote alveolar bone remodeling on the compression side. Although the difference of tooth movement over 14 days between the two groups was not statistically significant; however, 660 nm PBM to accelerate bone remodeling is stronger than 830 nm PBM at an early stage.