Abstract
The surgical treatment for preventing severe atrophy of the alveolar ridge caused by extraction of a tooth or cystectomy has improved considerably because of a development of calcium phosphate implant materials, in particular hydroxyapatite (HA), which has been shown to be bioactive in hard tissues. Histological studies have demonstrated that HA directly bonds with a bone after implantation. However, there has been no accurate answer to the question why HA shows bioactivity. In addition, numerous studies show that alveolar ridge augumentation utilizing HA granules does not always produce good results. Attempts to overcome these questions and clinical disadvantage have been made by a biochemical study of initial calcification of HA surrounding tissues and by a clinical study of sintered bone (TBC)-collagen complex. 1. Matrix vesicles were isolated from the epiphysial growth plate of young rabbits. Lactate dehydrogenase (LDH) activity was detected in the isolated matrix vesicles only in the presence of detergents. The isolated matrix vesicles contained all five LDH isoenzymes but not other cytosolic enzymes. These results show that LDH is located in the matrix vesicles. 2. Non-enzymatic phosphatase activity was detected in HA. Among different types of HA, biological HA (sintered bone ; True Bone Ceramic) showed the highest activity. 3. True Bone Ceramic (TBC)-collagen complex was prepared. Collagen serves as an adherent for the HA particles, resulting in a material that is easy to handle in the augumentation of a bone. 4. In a primary culture of chicken growth chondrocytes, TBC-collagen complex promoted cell growth and cell differentiation. 5. The healing process of TBC implanted dental extraction sites in mongrel dogs was histologically evaluated with and without the use of collagen. At 4 weeks after implantation of TBC-collagen, numerous immature osteoids were observed in the central area of extraction sites. At 12 weeks, TBC-collagen showed good ossification at the extraction sites where cortical bone had existed.
