Pj. Li et al., THE ROLE OF HYDRATED SILICA, TITANIA, AND ALUMINA IN INDUCING APATITEON IMPLANTS, Journal of biomedical materials research, 28(1), 1994, pp. 7-15
Pure soluble silica prepared by a sol-gel method induced bone-like hyd
roxyapatite formation onto its surface when the silica was immersed in
a simulated body fluid (SBF), whereas silica glass and quartz did not
. This finding directly supports the hypothesis that hydrated silica p
lays an important role in biologically active hydroxyapatite formation
on the surfaces of bioactive glasses and glass-ceramics, which leads
to bone-bonding. Gel-derived titania is also a hydroxyapatite inducer
because of its abundant TiOH groups. These results provide further ins
ight into the unique osseointegration of titanium and its alloys. It i
s suspected that gel-derived titania develops an apatite layer by taki
ng calcium and phosphate from the body fluid, thus producing bone-bond
ing. Although sufficient A1OH groups may remain in the alumina gel, th
ey do not serve to initiate apatite generation when immersed in SBF. T
his phenomenon explains the fact that an intermediate fibrous tissue i
s usually found to separate the alumina implant from bone. One may inf
er that both abundant OH groups and negatively charged surfaces of gel
-derived silica and titania are important for hydroxyapatite induction
. Material which possesses and/or develops both a negatively charged s
urface and abundant OH groups in a physiologically-related fluid is mo
st likely to be an efficient apatite inducer. Such materials are suita
ble candidates to serve as bone-bonding biomaterials. (C) 1994 John Wi
ley and Sons, Inc.