Cogrinding significance for calcium carbonate-calcium phosphate mixed cement. II. Effect on cement properties

In the present study, we aim to evaluate the contribution of the cogrinding process in controlling calcium carbonate-dicalcium phosphate dihydrate cement properties. We set a method designed to evaluate phase separation, usually occurring during paste extrusion, which is quantitative, reliable, and discriminating and points out the determining role of cogrinding to limit filter-pressing. We show that solid-phase cogrinding leads to synergistic positive effects on cement injectability, mechanical properties, and radio-opacity. It allows maintaining a low (<0.4 kg) and constant load during the extrusion of paste, and the paste's composition remains constant and close to that of the initial paste. Analogous behavior was observed when adding a third component into the solid phase, especially SrCO3 as a contrasting agent. Moreover, the cement's mechanical properties can be enhanced by lowering the L/S ratio because of the lower plastic limit. Finally, unloaded or Sr-loaded cements show uniform and increased optical density because of the enhanced homogeneity of dry component distribution. Interestingly, this study reveals that cogrinding improves and controls essential cement properties and involves processing parameters that could be easily scaled up. This constitutes a decisive advantage for the development of calcium carbonate-calcium phosphate mixed cements and, more generally, of injectable multicomponent bone cements that meet a surgeon's requirements. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 99B: 302-312, 2011.