Abstract: Objective:To observe the orthodontic tooth movement after regeneration of Beagl dog's periodontal tissue defect with biphasic calcium phosphate(BCP), and to elucidate the mechanism of BCP as a scaffold material for periodontal regeneration. Methods:Six adult male Beagle dogs were selected;the right upper quardrant(B) and the left lower quardrant(D) regions of each dog were used as blank control group, and the left upper quardrant(A) and the right lower quardrant(D) regions were used to establish the dog models of periodontal tissue defect of bilateral incisors. BCP was implanted into the defect to regenerate the defect. After 12 weeks of BCP implantation into the defect for defect tissue regeneration, the orthodontic tooth movement models were established (experimental group). Stress stimulation was applied in experimental group and control group, respectively. Two Beagle dogs were randomly executed at 1, 2 and 4 weeks after loading. The specimens were stained, the histological changes of regenerated periodontal tissue and the expression of core binding factor α1(Cbfα1) regulating osteogenesis under stress were observed;the changes in normal periodontal tissue under the same stress were observed. Results:The Masson staining results showed that the periodontal ligament of the dogs in experimental group and control group became narrower and denser at 1 week after stress stimulation; the alveolar bone of the dogs in dogs in experimental group was mainly blue; the alveolar bone of the dogs in control group was generally red except for the compression area of the periodontal ligament. At 4 weeks after stress stimulation, the alveolar bone of the dogs in experimental group was red-blue, while the alveolar bone of the dogs in control group was red; the blood vessels in periodontal ligament of the dogs in two groups were rounded. One week after stress stimulation, the alveolar bone surface of the dogs in experimental group and control group was covered with bone resorption lacunae containing the multinucleated osteoclasts, the cytoplasmic Cbfα1 staining was positive, and the compressed and deformed periodontal ligament cells were arranged disorderly. Four weeks after stress stimulation, the osteoclasts disappeared in experimental group, and the bone resorption lacunae was filled by osteoblasts, and the osteoblasts on the other side of the trabecula were also active; the expression of Cbfα1 was still found in the bone marrow mesenchymal cells and the marginal osteoblasts of alveolar bone. The expression of Cbfα1 was weak in control group. Conclusion:The periodontal tissue regenerated by BCP has reached the normal periodontal tissue. Under the action of orthodontic force, it has normal osteogenesis function and can complete the bone remodeling process of orthodontic tooth movement.

Key words: biphasic calcium phosphate, periodontal regeneration, orthodontic tooth movement, core-binding factor