ABSTRACT
Objective To explore the feasibility of He-Ne laser irradiation in promoting orthodontic tooth movement and periodontal remodeling through observing the effect of low power laser on the expression and distribution of matrix metalloproteinases- 9(MMP- 9) during orthodontic tooth movement in rabbit. Methods Thirty rabbits were divided into 1d,3d,5d,7d,14d and 21d groups, each group were given a coil spring connected to the maxillary upper first molar to the upper incisor and fixed bilaterally by a ligature wire and set force to 80g. He-Ne laser irradiation was performed on the right side of the orthodontic tooth, and the left side served as control. Radiation time ranged from 1 day to 5 days, once a day, 15min each time. All of the tissue sections were proceeded with MMP- 9 immunohistochemical staining. MMP- 9 average gray scale in periodontal tissue of the orthodontic teeth was analyzed by a Computer Image Analyzing System. Results The expression level of MMP- 9 increased earlier and lasted for a longer time in the compression and tension area on the side of irradiation by He-Ne laser as compared to those on the control side. There was significant difference between the irradiation side and the control side in terms of the MMP- 9 expression gray scale in the tension zones at 5 and 7 days post-operation, and in the pressure zones at 3,5,7 day post-operation. Conclusion During the movement of orthodontic teeth, local irradiation with He-Ne laser could increase the expression of MMP-9. It was suggested that the irradiation with low power laser accelerate blood vessel and bone remodeling.