Abstract: BACKGROUND: In clinic, guided bone regeneration technology is often used to reconstruct the bone defect. That is, the scaffold material is implanted in the bone defect, and then the biological barrier membrane is used to establish a stable environment to ensure the proliferation of osteoblasts and the formation of blood vessels, which has achieved good results.  
OBJECTIVE: To observe the osteogenic effect of true bone ceramic combined with acellular dermal matrix in tooth socket filling.
METHODS:  Bovine cancellous bone was calcined to true bone ceramic. The acellular dermal matrix was prepared from split-thickness skin which the epidermis and cellular components have been extracted. Cytotoxicities of true bone ceramic and acellular dermal matrix were evaluated by MTT assay. The second and fourth premolars on both sides of the mandible were extracted in nine beagle dogs. The true bone ceramic was implanted into the socket and covered with acellular dermal matrix. The buccal and lingual gingivae were separated and sutured to close the extraction wound. At 1, 3, and 6 months after surgery, cone beam CT, X-ray and histology were used to evaluate the new bone formation. The experiment was approved by Drug Safety Evaluation Center in China Institute for Radiation Protection (approval No. CIRP-IACUC-(R)2018081).  
RESULTS AND CONCLUSION: (1) L929 mouse fibroblasts were cultured with the two extracts for 24 hours. Under the inverted microscope, the cells were in good shape without vacuoles or death. MTT assay results showed that the cell survival rate was above 85%, without obvious cytotoxicity. (2) The results of cone beam CT showed that the relative gray value of the implant site increased gradually with the extension of healing time, and the amount of bone formation in tooth extraction wound increased. (3) The X-ray films showed that at 1 month after the operation, the imaging of the implanted site was uniform without obvious osteogenesis. At 3 months after the operation, there was partial osteogenesis. At 6 months after the operation, the implant site had obvious osteogenesis. (4) Hematoxylin-eosin staining showed that a large number of trabeculae were formed 1 month after operation, and the bone trabeculae was evenly arranged, and the true bone ceramic was partly absorbed. Coarse trabeculae structure with a large amount of cartilage and a small amount of calcined bone remained at 3 months after operation. The tooth extraction wound was nearly healed and mature bone tissue was formed, and the bone unit structure was visible; true bone ceramic could not be seen at 6 months after operation. (5) Results suggest that true bone ceramic combined with acellular dermal matrix show good bone formation for extraction socket filling.

Key words: material, true bone ceramic, acellular dermal matrix, extraction socket filling, guided bone regeneration