Tracking the initial stage of bioactive layer formation on Si-Ca-Na-P oxide glasses by nanoindentation

Bioactivity of a newly formulated glass composition is assessed based on qualitative information of X-ray diffraction, spectroscopic or electron microscopic data of the surface layer formed during soaking in simulated body fluid (SBF) under physiological temperature, pH and CO2 partial pressure. In our experiments we use an alternative method, nanoindentation testing to reveal compositional dependence of bioactivity in a series of SiO2(45)CaO(25)Na2O(30-x)P2O5(x) glasses, where x = 0,1,3,5.
According to our results, analytical evaluation of nanoindentation data, namely the variation of Vickers hardness and Young modulus as function of composition, allows quantitative description of bioactive layer formation already in the very early stage of the reaction. These results can be reproduced from the data provided in this contribution.