Apatite-wollastonite-containing glass-ceramic (A-W . GC) has a strong
ability to bond to bone and relatively high mechanical strength. There
fore, as a bulk material it has recently been applied clinically even
in load-bearing sites. In this study, we modified A-W . GC by altering
its composition ratio with the removal of CaF2 and the addition of B2
O3, and examined the potential use of the resulting new glass-ceramic
as a material for coating on a titanium (Ti) alloy. The bioactivity of
this new coating (NC) material and its bonding ability to bone were i
nvestigated mechanically and histologically. After implantation of the
Ti alloy plate coated with this material into the tibiae of rabbits f
or 2, 3, 4, 8, and 25 weeks, a detaching test was performed. The detac
hing failure load of the NC plates was compared with those of A-W . GC
plates, hydroxyapatite (HA) plates, and uncoated Ti alloy plates impl
anted in the same way. The failure load of NC was as high as that of A
-W . GC for all periods, whereas it was significantly higher at 3 and
4 weeks than that of HA. Uncoated Ti alloy showed lower failure loads
for all periods, differing significantly from the other materials. The
re was no breakage or detachment of the coating layer observed after t
he detaching test. Histological examinations by CMR, Giemsa surface st
aining, and SEM-EPMA showed that NC bonded directly to bone without an
y intervening soft tissue layer. A calcium-phosphorus-rich layer (apat
ite layer) was observed within the coating layer, as is the case in A-
W . GC. These results indicate that this new glass-ceramic has earlier
bone-bonding ability and high mechanical strength, making it a promis
ing coating material. (C) 1993 John Wiley & Sons, Inc.