Abstract: Objective: To investigate the role of high mobility group box-1 (HMGB1) during orthodontic tooth movement. Methods: Thirty Wistar rats were randomly divided into 0, 1, 3, 5 and 7d group. Left maxillary 1st molars were protracted by a force of 0.6N, whereas orthodontic appliances were placed but orthodontic force was not applied on the contral lateral 1st molars. HE staining was utilized to observe the morphology of periodontal tissue during tooth movement, and immunohistology was used to detect HMGB1 expression by evaluating average optical density. Results: Typical histological features were observed in the periodontal tissue around upper molars, with narrowed periodontal ligament, disarranged periodontal fibers and increased osteoclasts in compression side, and widened periodontal membrane, extended periodontal fibers and increased osteoblasts in the tensile side. Expression of HMGB1 reached the lowest point (0.0012±0.0009) on 1st day on the compression side, which was significantly lower than control (0.0239±0.011), and increased gradually from 1st day to 7th day, peaking at 0.0127±0.0014 on 7th day. Expression of HMGB1 decreased on the 1st day (0.0193±0.0012) on the tensile side, which was lower than control group (0.0284 ± 0.009), and reached the highest point on 5th day (0.0324±0.0014), which was not significantly different from control group (0.0289±0.0012). Conclusion: Excessive orthodontic force reduced HMGB1 expression in periodontal membrane and decreased hyaline tissue clearance and tooth movement.

Key words: Orthodontic tooth movement, High mobility group box-1, Bone remodeling