Effect of the laser and light-emitting diode (LED) phototherapy on midpalatal suture bone formation after rapid maxilla expansion: a Raman spectroscopy analysis

The aim of this study was to analyze the effect of laser or light-emitting diode (LED) phototherapy on the bone formation at the midpalatal suture after rapid maxilla expansion. Twenty young adult male rats were divided into four groups with 8 days of experimental time: group 1, no treatment; group 2, expansion; group 3, expansion and laser irradiation; and group 4, expansion and LED irradiation. In groups 3 and 4, light irradiation was in the first, third, and fifth experimental days. In all groups, the expansion was accomplished with a helicoid 0.020" stainless steel ortho- dontic spring. A diode laser (λ780 nm, 70 mW, spot of 0.04 cm 2 , t=257 s, spatial average energy fluence (SAEF) of 18 J/cm 2 ) or a LED (λ850 nm, 150 mW±10 mW, spot of 0.5 cm 2 , t=120 s, SAEF of 18 J/cm 2 )w ere used. The samples were analyzed by Raman spectroscopy carried out at midpalatal suture and at the cortical area close to the suture. Two Raman shifts were analyzed: ∼960 (phosphate hydroxyapatite) and ∼1,450 cm −1 (lipids and protein). Data was submitted to statistical analysis. Significant statistical difference (p≤0.05) was found in the hydroxyapatite (CHA) peaks among the expansion group and the expansion and laser or LED groups. The LED group presented higher mean peak values of CHA. No statistical differences were found between the treated groups as for collagen deposition, although LED also presented higher mean peak values. The results of this study using Raman spectral analysis indicate that laser and LED light irradiation improves deposition of CHA in the midpalatal suture after ortho- pedic expansion.