Human osteoblast response to photobiomodulation
Objectives: Photobiomodulation is a non-invasive method for accelerating orthodontic tooth movement. Photobiomodulation is known to increase the rate of tooth movement by more than 2-fold compared to conventional techniques. The mechanism of action at the cellular level, however, remains unclear. The aim of this study was to investigate the effect of photobiomodulation on the proliferation and mineralization of human osteoblasts in vitro.
Methods: Human osteoblasts were seeded and cultured in a concentration of 104 cells per well. A near infrared light source with a continuous wavelength of 850 nm and a power density of 60 mW/cm2 was used to irradiate the cell layer directly, with a distance of 2.5 cm below the plate. The sample were divided into 3 groups per plate: Group 1– 1 minute daily radiation for 9 days; Group 2– 10-minute radiation only at Days 1 and 5; and Group 3– control (no radiation). MTT assay was used to study the proliferation and viability of cells for 9 days over the course of the experiment (5 weeks). Alkaline phosphatase (ALP) activity was measured once a week.
Results: Photomodulation increased osteoblast proliferation in a dose-dependent manner. 10 minutes radiation resulted in a significantly higher proliferation compared to control and 1 minute radiation (p<0.05). At day 5, proliferation in Group 1 was 1.8-fold higher than the control and remained higher up to day 8 (p<0.05). After day 8, all groups showed a decrease in proliferation. Photobiomodulation also dose-dependently increased the ALP activity, which was higher for Group 2 during the first 3 weeks. At week 5, however, 1 min radiation resulted in the highest ALP activity (1.8-fold higher than Group 2 and 4.4-fold higher than the control; p<0.05).
Conclusion: The data suggests that photobiomodulation stimulates the proliferation and mineralization of human osteoblasts by modulating their activity.