The effect of CHA on extraction alveolar Macroscopic observation: Three months postoperation, inspection report showed that the shape of the alveolar was enough. And there was no obvious height decrease of alveolar compared with adjacent socket ridge.   X-ray observation: 11 patients with 17 sockets were all valid. The sclerotin at graft area increased obviously, and the image of sclerotin density evenly distributed. Uniform structure of bone trabecula could be seen from the image, which integrated the bone tissue with bone graft material, and the boundaries almost disappeared. All socket sites had enough new bone and did not require bone graft again. Before teeth extraction, the distance between alveolar crest and incisal edge of adjacent teeth was (8.17±0.18) mm, and after bone graft, the distance was (8.23±0.19) mm, showing no statistically significant difference (P > 0.05). The results showed that there was no obvious absorption of alveolar bone before and 3 months after the experiment (Table 1)."

Typical cases For a male patient, 24 years old, maxillary central incisor was injured because of traumatism. Residual roots were extracted immediately with mini-invasive surgery under local anaesthesia. After cleaning out the operation area we transplanted hydroxyapatite bioceramics bone in extraction socket, and overlapped tooth extraction wound with a full thickness free mucosal flap, sutured without tension. The examinations were done at periodic intervals at 3 and 6 months after the surgical procedure (Figure 1).   Before the tooth extraction, the alveolar bone height of   maxillary central incisors was cow. At the same time, CHA was placed in socket site. Three months after extraction, wound healing was good, similar structure of bone trabecula that integrated the bone tissue with bone graft material could be seen, and the boundaries almost disappeared. The bone invagination in the alveolar ridge was significantly reduced, approximate to the height of alveolar bone crest adjacent. Then, dental implant was transplanted. Three months after implantation, the implant was fused well with surrounding bone tissue, and there was no significant absorption of alveolar bone that healed well.   Adverse effects The 17 sockets in 11 patients were all clinically healed. In addition to the local mild swelling, no bone debris or purulent materials appeared. The patients felt fine during recovery periods. "