Apatite formation on the surfaces of various silica gels prepared in different media and silica glass was investigated in SBF1.5Ca. After the soaking in SBF1.5Ca for 7d, the bonelike apatite was formed on the surfaces of all the silica gels having abundant silanol groups. It was not, however, formed on the surface of the silica glass having little silanol groups even after the soaking for 2 weeks. From the results, it can be concluded that all the kind of silanol groups developed on the silica gels can induce the apatite nucleation, although there is some differences in their nucleating abilities. It is interesting to know what type of the silanol groups is most effective for the apatite nucleation. Unfortunately, however, Raman spectra in Fig. 1 give no information about difference in surface structure among the gels. Further study is needed for revealing the most effective structural unit.
