Abstract: Objective: To study the effects of orthodontic timing (2 and 12 weeks) on tooth movement speed and periodontal tissue regeneration, and to evaluate the response of periodontal tissue to orthodontic force. Methods: A periodontal bone defect model in Bama miniature pigs was established. Platelet-rich fibrin (PRF) combined with periodontal bone grafting was used to treat bone defect. Orthodontic traction was carried out at 2 and 12 weeks after regeneration. Animals were sacrificed after 6 weeks of orthodontics. Periodontal parameters, micro-CT, histomorphology, and immunohistochemistry were examined. Results: Compared with 12 weeks after regeneration, the orthodontic group at 2 weeks after regeneration had a faster tooth movement speed (P=0.025). Positive correlations of bone mass included higher relative bone volume, number of bone trabecular and thickness of bone trabecular (P=0.019, P=0.014, P=0.024). Negative correlations of bone mass: trabecular segregation, ratio of bone surface area to bone volume, and trabecular mode factor were lower. (P=0.033, P=0.029, P=0.008). Orthodontic bone remodeling was more active, new bone mass was more, and the expression levels of osteoprotegerin and bone morphogenetic protein 2 were higher (P=0.006, P=0.015). Conclusion: Two weeks after periodontal regeneration, the orthodontic teeth move faster, new bone formation is more, and the expressions of osteoprotegerin and osteogenic protein are higher.

Key words: bone grafting, platelet-rich fibrin, orthodontic, Micro-CT, immunohistochemistry