ABC (アパタイト-生体活性ガラス複合体) の表面の性質が曲げ強度に及ぼす影響

抄録

Apatite-biologically active glass composite (ABC) was synthesized and its microstructure, bioactivity and bending strength were studied. The existence of fluorapatite (FAp), Na₂Ca₂Si₃O₉ and the remainder glass was confirmed by XRD and SEM. From in vitro experiment, rapid formation of stable FAp film in 7 days was observed by IRRS, SEM and EPMA. Bending strength of ABC increased slightly with treatment time in trisaminomethane buffer solution to 30 days while under similar condition the strength of sintered hydroxyapatite (HAp) decreased gently. The increase of bending strength of ABC was closely related with the surface ion migration to form FAp. Radical crack tip blunting due to ion migration and/or stress releasing around tip was considered to be the main reason. From in vivo experiment, the bone bonding strength of ABC was 27MPa, higher than that of sintered HAp. The bone bonding strength, in this case, is equivalent to the fracture shear strength between bone and material after implantation in rabbit femur during 8 weeks. Furthermore, just the same as the result of in vitro experiment, FAp film formation on the surface of ABC was also observed in vivo, which suggested the possibility of slight increase of bending strength in living body. For clinical application as bone replacement or tooth implant, possible advantage of ABC regarding bending strength is expected to be (1) strength increase and (2) strength recovery after introduction of a new crack, during implantation in living body.