Incorporation of a controlled-release glass into a calcium phosphate cement

A so-called controlled-release glass was synthesized occurring in the syste m CaO-Na2O-P2O5. A certain sieve fraction of this grass was incorporated in a calcium phosphate cement, of which the powder contained alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate (DCP) and precipitated hydroxya patite (HA). The glass appeared to retard the cement setting slightly and i t reduced considerably the compressive strength after aging in aqueous solu tions which were continuously refreshed. Scanning electron microscope (SEM) pictures and X-ray diffraction (XRD) patterns of the samples after 5 weeks of aging showed that the glass was not dissolved but that large brushite c rystals were formed. Thereby, aging in CaCl2 solutions resulted in more bru shite formation than aging in NaCl solutions. The brushite crystals did not reinforce the cement. Neither was the aged glass-containing cement weaker than it was before the brushite formation right after complete setting. In conclusion, the incorporation of controlled-release glasses into a calcium phosphate cement and subsequent aging in aqueous solutions did not result i n the formation of macropores in the cement structure, but that of brushite crystals. This incorporation reduced the compressive strength of the cemen t considerably. (C) 1999 Kluwer Academic Publishers.