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The work is devoted to investigation of porous glass-ceramic composite materials on the basis of biogenic hydroxyapatite and sodium borosilicate glass prepared from starting powders with different particle sizes (<50 ?m and <160 ?m). Starting hydroxyapatite/glass weight ratio was 1.0/0.46 and sintering temperature was ~800?C. Microstructural characterization of the surface and fracture of the samples revealed a decrease in sizes of grains and pores with decreasing the particle size of the precursor powder. However, porosity of the composites practically did not depend on the particle size and was equal to 32.5-33.0%. The same tendency was observed for the compression strength (66-67MPa). However, investigation of structural-mechanical properties using an indentation method, where dominant load is applied to the surface layers of sample, showed up the effect of the particle size of the starting powder on the mechanical properties of the composites: the smaller particle size, the higher mechanical properties.

This in vitro investigation of the behavior of two types of calcium phosphate glass ceramics on the basis of phosphates of biogenic or synthetic origin prepared from initial mixtures with different particle size has revealed that some different factors affect the behavior, namely the phase composition of composite, fraction of open porosity, and average diameter of pore channels. It was established that the solubility of the composites on the basis of synthetic calcium phosphates and glass after 2 and 7 days contact with saline composites is the highest among the materials under study. First of all, this fact is related to the peculiarities of their phase composition, high fraction of open porosity, and high permeability. As for biogenic hydroxyapatite/glass materials, their solubility is several times lower in spite of close total porosity. The particle size of initial mixture practically does not affect the material solubility; the latter is only slightly lower for smaller particles.

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