[Histological study of hydroxylapatite mixed with collagen as osseous implant in mandible].

By using five Taiwan Macaca monkeys as experimental animals, three bony defects about 5 x 5 x 3 mm in size were created at each of their buccal region of mandible. Bovine skin collagen and particulate hydroxylapatite were used as implant materials. The artificial defects implanted with hydroxylapatite/collagen mixture were experimental group and the defects implanted with collagen or without any implantation were control groups. The monkeys were sacrificed at the time of 1,2,3,6,9 months after implantation surgery and were injected with tetracycline according to the above intervals at one week before being sacrificed. The specimens were divided into two parts, one of which was decalcified and stained with hemotoxylineeiosin for observation under optic light microscope, the other without decalcification was made into ground section for observation under fluorescent microscope. The result revealed that the healing processes of the two control groups were similar with each other. Bone formation was delayed in HA/Collagen group because it took almost five months to achieve complete bony repair of the mandibular defect. However bone formation at the HA/Collagen implant site was earlier than that at the pure HA implant site in our similar study. What's the role of collagen that played during bone formation still needed further investigation. The tissue response was good without obvious inflammatory cells infiltration. Clinical application of block form of dried HA/Collagen mixture was suggested for it was easier to handle and could decrease the flow of HA particles after implantation.