Osteoconductive Property of Locally Synthetic Hydroxyapatite from Egg Shell

Objectives: To formulate and evaluate the osteoconductive property and healing potential of locally synthetic hydroxyapatite from egg shell in extraction sockets. Methods: The preparation of hydroxyapatite involved drying and thermal decomposition of egg shell, followed by hydrothermal reaction at low temperature with diammonium hydrogen phosphate and water. The powder was compacted at pressure of 80 kg/cm2 and sintered at temperature of 900-1300^oC. The toxicity was tested on fibroblasts and osteoblasts. The upper central incisors of 36 adult Sprague Dawley rats were extracted, and the extraction sockets were divided into four groups: the sockets of Group 1 (Control) were left empty; those in Group 2 were filled with commercially available hydroxyapatite; and the Group 3 was treated with the synthetic hydroxyapatite from egg shell; while the Group 4 was treated with the synthetic hydroxyapatite and growth factors from platelet rich plasma. All sockets were sutured with resorbable dental suture. Animals were sacrificed, 2, 3 and 4 weeks after tooth extractions. Serial sections were obtained and stained with hematoxylin and eosin, immunohistochmistry (Osteocalcin), and Massons Trichom staining. Blood samples were taken before and after the experiment for biochemical analysis. Results: The hydroxyapatite from egg shell showed no cytotoxicity. There were no changes in the biochemical blood parameters of experimental group. Histological examination demonstrated that the sockets (Group 4) treated with the synthetic hydroxyapatite and growth factors were completely filled with newly generated bone tissue with a thickness comparable to native bone, and they were significantly better than the control group (3.60±0.12, 12.68±0.52, p<0.05).  Fibroblasts and collagen fibers were more predominant in experimental groups than the control (fibroblasts 1.68±0.14, 0.83± 0.04, collagen fibers 8.07±0.05, 5.47±0.07, p<0.05). Conclusion: This study suggests that the locally synthetic hydroxyapatite from egg shell in combination with growth factors could promote bone healing through improving osteoconductive property.