骨適合性を有する多相系生医学材料に関する研究

第2報ハイドロキシアパタイト-合成高分子複合材料の生体内組織反応について

抄録

Regarding hydroxyapatite [HAP]-polymer-metal multiphase material developed as a substitute for the hard tissue repairing tooth and bone defects and their reconstruction, a study was made on soft-tissue and bone-tissue reactions of the HAP-polymer composite material, namely, on its facets in direct contact with the living body.For the HAP-polymer composite material, poly (2, 2, 2-trifluoroethyl methacrylate)[PTFEMA] or poly (methyl methacrylate)[PMMA] containing 70 wt% of HAP particles (mean 8 μm or 70 μm) was prepared. As controls, both homopolymer and HAP ceramics block were used.These were implanted subcutaneously in rats and in the tibiae of adult dogs for soft X-ray and histological observations and contact microradiograph for 6 months.
Subcutaneous implantation: One week after the implantation of each material, all of the test pieces showed encapsulation by the granulation tissue accompanied by mild to mediocre inflammatory cell infiltration.In 3 months and thereafter, inflammatory reaction was scarcely observed in the periphery of the materials, and the test pieces were surrounded by the fibrous capsules, showing a trend that, with polymer composite material and HAP ceramics block, inflammatory cell infiltration disappears at an early stage as compared with the homopolymer.
Intraosteous implantation: 1) It was observed that new bone formation with the homopolymer started from the endoseal bone surface away from the test piece, and presence of the fibrous tissue was seen between the test piece and the bone throughout the period. 2) Polymer-HAP 70 wt% composite material showed a bone affinity almost as high as that of the HAP ceramics block.That is, new bone formation started from the surface and periphery of the test piece, and after 3 months bone formation was seen without the presence of fibrous tissue.3) The HAP-S particular composite material group exhibited evidence that its contact with bone becomes uniform at an early stage as compared with the HAP-L particular group.No difference was observed in bone tissue reaction between the PMMA and PTFEMA composite material groups, but PTFEMA is presumed to be superior if its physical and mechanical properties and adaptability to HAP particles are taken into consideration.
Thus, it was found that the multiphase material, in which core metal is used and PTFEMA+HAP-S 70 wt% composite material are placed on the interface with the bone, is useful as a substitute material for hard tissue for its bone compatibility both biologically and mechanically.