Abstract: Objective To study the dynamic changes of RNAKL/OPG expression in orthodontic alveolar bone remodeling and its effects on osteoclast formation and bone tissue remodeling. Methods the left maxillary orthodontic model of mice was established and observed continuously on day 5, day 7, day 14 and day 21 after orthodontic treatment. The distance of first molar movement and the change of alveolar bone in distal root pressure were analyzed by Micro CT. HE staining and TRAP staining were used to detect the histological and osteoclastic changes of the distal root pressure side at different time points. The expression of RANKL,OPG and Caspase3 were detected by immunohistochemical staining and immunofluorescence staining at different time points.Results after the orthodontic force was applied, the distance between the left first molar and the second molar increased gradually, and the expression of RNAKL and OPG increased gradually in the distal root pressure side of the first molar, and the expression of RANKL reached a peak on the 7th day after the application of orthodontic force. Then the peak of OPG expression appeared on the 14th day, the expression peak of RANKL was earlier than that of OPG, and accompanied by osteoclast formation peak. At the same time, the number of apoptosis in periodontal tissue increased gradually, tooth movement was obvious. Conclusion During orthodontic treatment, the expression changes of RANKL/OPG showed temporal characteristic changes, accompanied by changes in the expression of key apoptotic molecules, and these changes were closely related to alveolar bone remodeling and tooth movement.

Key words: Orthodontic force, Bone remodeling, RANKL/OPG, Caspase3