ジルコニア分散ヒドロキシアパタイトセラミックの基礎的研究

分散比による骨親和性と骨接着強度の比較検討について

抄録

To evaluate the effect of zirconia concentration on the characteristics of candidate bioceramic materials, the mechanical properties and biocompatibility of zirconia dispersed hydroxyapatite ceramics (Zr-HAs) containing 1.6, 50 and 65vol% of zirconia were examined and compared with those of hydroxyapatite ceramic (HA), partially-stabilized zirconia ceramic (PSZ), titanium (Ti), and cobalt-chrome alloy (Co-Cr).
The bending strength and fracture toughness of all Zr-HAs were higher than those of HA, and these variables increased parallel to the zirconia concentration.On the other hand, Young's modulus of all Zr-HAs was lower than that of HA.
In order to examine the affinity for bone, the materials were implanted into die femurs of rats and specimens were taken periodically.Histological examination, contact microradiography, scanning electron microscopy (SEM) and energy dispersion X-ray microanalysis (EDXA) revealed that the patterns of bone formation around the implanted Zr-HAs and Ti were similar to that of HA, showing direct contact with the newly formed bone.
To evaluate bonding strength to bone, Zr-HAs, HA, PSZ and Ti were implanted into tibias of adult mongrel dogs.Three months after implantation, bonding strength was examined by a push-out test.The values for the bonding strength of Zr-HAs were significantly higher than those of PSZ or Ti (p<0.01).Bonding strength decreased when higher concentrations of zirconia were contained in the ceramics.SEM and EDXA analyses of the implanted Zr-HAs after the push-out test revealed fracture sites beneath the surface of newly formed bone or at the interface between the materials and bone.For implanted HA, fractures sites were situated within the implant, within the bone, or at the interface between implant and bone.On the other hand, in the case of PSZ and Ti, fracture sites were noted in the connective tissue layer or at the interface between the implant and bone.
In conclusion, although the mechanical properties of Zr-HAs were dependent on the concentration of zirconia, each Zr-HA evaluated in this study showed excellent mechanical strength, bone affinity and bonding strength.The results suggest that Zr-HAs are desirable ceramics for clinical use.