Application of Calcium Phosphate Ceramics to Periodontal Therapy: 5. Application of Hydroxyapatite Block for Wide Artificial Bone Defect

The aim of this study was to investigate the biocompatibility and the osteoconductivity of hydroxyapatite block (HAP-B), prior to its clinical use as bone graft material for one wall or horizontal bone defects. To observe HAP-B's biocompatibility, hydroxyapatite granules (HAP-G), of which HAP-B was made, were implanted into left M. rectus femoris of rats. Each rat was sacrificed two, four, twelve and twenty-four weeks after implantation. Further HAPB's osteoconductivity was researched. Previous to implantation, both sides of P2 and P4 in beagle dogs were extracted. Three months after extraction, artificial bone defects were prepared at the mesial sites of P3 and M1. HAP-Bs were implanted into the mesial sites of M1 and not into those of P3 as control. Two, four, eight and twelve weeks after implantation, beagle dogs were sacrificed and their mandibles were biopsied for light microscopic study. The results obtained were as follows. 1. All through the experimental period, HAP-Gs had been encapsulated by fibrous connective tissue involving foreign body giant cells and/or macrophagelike mononuclear cells. But HAP-Gs had been isolated from muscular tissues which showed no damage. 2. There were no pathological findings in liver, spleen, kidney, heart, lung and adrenal gland in rats. 3. The wound healing of subepithelial connective tissue and alveolar bone was almost finished twelve weeks after implantation in both control and experimental sites. 4. Newly formed bone tissues and osteoids attached directly to HAP-B and woven bone formation was noted also in connective tissues among HAP-B. 5. The external form of the regenerated alveolar bone of control showed a hollow at mesio-distal center, but that of experimental site was similar to anatomical feature. Haversian systems existed also in the regenerated alveolar bone involving HAP-B. Considering above-described results, HAP-B had fine biocompatibility and osteoconductivity, and brought more natural feature to bone repair. Consequently HAP-B were much expected to be effective on clinical use as bone graft material.