Abstract
To improve mechanical strength of bioglass, it is considered to use the glass as a coating material to alumina, but the difference in thermal expansion coefficient between two materials is too high to make a good coating. The aim of the present study, therefore, is to find out proper glass composition matching its thermal expansion coefficient to that of alumina without losing biocompatibility. In the present work, various glasses were prepared by substituting B2O3 and CaO for Na2O in the glass system of 55.1%SiO2-2.6%P2O5-20.1%Na2O-13.3%CaO-8.9%CaF2 (in mole%), and the thermal expansion property and reaction property in tris-buffer solution for the resulting glasses were measured. The thermal expansion coefficient of the glass was decreased with the substitution of B2O3 for Na2O, and it became close to that of alumina in the glass in which 8 mole% of CaO was substituted for Na2O. Hydroxyapatite formation was enhanced and silica rich layer thickness was decreased with B2O3 substitution for Na2O. CaO substitution for Na2O didn't deteriorated the hydroxyapatite development.