Apatite Forming Ability and Dissolution Behavior of Boron- and Calcium-Modified Silicon Oxycarbides in Comparison to Silicate Bioactive Glass.

The bioactivity of Ca and/or B modified silicon oxycarbides has been assessed upon immersion in SBF (simulated body fluid). In the context of the present work, bioactivity refers to the likeliness of hydroxyapatite crystallization (biomineralization) on the surface of a material when in contact with physiological fluids. The incorporation of Ca and B into the silicon oxycarbide glass network is found to increase its bioactivity, which seems to scale with the content of Ca; thus, glass with a relatively large Ca/Si molar ratio (i.e., 0.12) is shown to exhibit bioactive characteristics similar to those of the benchmark silicate bioactive glass of composition. The release kinetics of the glasses modified with Ca and/or B during the SBF test was studied by inductively coupled plasma-optical emission spectroscopy. It has been observed that the Si release kinetics can be correlated with the Ca content in the glasses: based glasses modified with Ca exhibited low Si release activation energies (i.e., 0.07 eV), being comparable to that of bioactive glass (i.e., 0.04 eV); whereas silicon oxycarbides without Ca modification showed higher activation energies for Si release (i.e., 0.27 eV).