Evaluating the effect of laser irradiation on bone regeneration in midpalatal suture concurrent to rapid palatal expansion in rats

BACKGROUND: Rapid palatal expansion is one of the most important orthopedic treatments that correct the dental and palatal constriction. Stability of the changes partly depend on the rapidity of new bone formation in affected sutures after expansion. The purpose of this study was to investigate the effect of laser irradiation on the healing of midpalatal suture concurrent to the expansion of midpalatal suture in rats. MATERIALS AND METHODS: A total of 78 male Sprague rats in seven groups were evaluated: A control group of six rats without any treatments and three experimental groups of 24 which underwent palatal expansion for different time periods (7, 14, and 30 days), and each divided into two groups of with and without laser irradiation. Laser therapy was done by gallium-aluminum-arsenide diode laser with 810 nm wavelength and 4 J/cm(2) irradiation in days 0, 2, 4, 6, 8, 10, 12, 14 in 4 points (1 labial and 3 palatal points). After sacrificing, the sections were evaluated by histomorphometric and quantitative analysis and results were statistically investigated by independent samples t-test. RESULTS: The results in 7 days, 14 days, and 30 days show that laser therapy can increase the rate of osteogenesis in palatal suture during rapid palatal expansion but the differences in 7 days groups were not significant (P = 0.117) while in 14 days groups (P = 0.032) and 30 days groups were significant (P = 0.001). Most of effectiveness of low-power laser was seen between 14 and 30 days while the laser therapy was stopped. CONCLUSION: These findings suggest that low-level laser irradiation can increase and accelerate bone regeneration in the midpalatal suture after rapid palatal expansion, hence, reduce retention time.