ULTRASTRUCTURAL-STUDY OF THE A-W GC-BONE INTERFACE AFTER LONG-TERM IMPLANTATION IN RAT AND HUMAN BONE

The interface between apatite- and wollastonite-containing glass-ceram ic (A-W GC) and bone after long-term implantation was studied by scann ing and transmission electron microscopy (SEM and TEM) using rat and h uman specimens. First, particles of A-W GC (100-220 mu m in diameter) were implanted into rat tibiae, and specimens were prepared for observ ation at 24, 48, 72, and 96 weeks after the operation. These long-term specimens showed an A-W GC-bone interface different from that at an e arlier stage, which was investigated in our previous studies. SEM show ed that the Ca-P-rich layer was wider, suggesting that leaching of ion s from the A-W GC had continued even after bonding with bone. In some regions, the material particles were evidently replaced by the bone. T EM showed that the intervening apatite layer had become indistinct, an d that A-W GC had intermingled with bone at the interface. In some reg ions, the surface of the A-W GC was degraded. These findings suggest t hat the surface region of A-W GC is slowly replaced by bone. Second, a human bone specimen, which included A-W GC particles (300-700 mu m in diameter) implanted as a bone filler for about 75 weeks was harvested and investigated. Excellent A-W GC-bone bonding was observed, and the ultrastructure of the interface was similar to that in rats after lon g-term implantation. This finding demonstrated that A-W GC possibly wo rked in human bone in the same way as in rat bone, showing excellent b ioactivity. (C) 1994 John Wiley and Sons, Inc.