EFFECTS OF IONS IN AQUEOUS-MEDIA ON HYDROXYAPATITE INDUCTION BY SILICA-GEL AND ITS RELEVANCE TO BIOACTIVITY OF BIOACTIVE GLASSES AND GLASS-CERAMICS

Hydroxyapatite induction by a synthesized pure silica hydrogel was exa mined in various simulated body fluids (SBFs) having different magnesi um, calcium, and phosphate ion concentrations as well as pH values. Th e silica hydrogel generated biologically active apatite on its surface by taking up calcium and phosphorous ionic groups from a surrounding SBF that was prepared to emulate the human plasma in inorganic composi tion. The induction period for apatite nucleation on the surface of th e silica was largely decreased with the addition of a small amount of the calcium or phosphate ions to the SBF and with an increase in pH, b ut increased with the addition of magnesium ion. Bioactivity of bioact ive materials like Bioglass(R) and glass-ceramic A-W was well interpre ted in terms of the rate of apatite formation reflected in these resul ts. Moreover, the results provide the basic knowledge for designing ne w bioactive materials. (C) 1993 John Wiley & Sons, Inc.