A novel injectable and degradable calcium phosphate/calcium sulfate bone cement

The aim of this study was to obtain a composite material which not only has suitable workability but also has excellent degradability. A novel injectable and degradable bone cement consisting of a mixture of calcium phosphate (α-tricalcium phosphate; α-TCP) and calcium sulfate dihydrate (CaSO 4 . 2H 2 O; CSD) powders as the solid phase and an aqueous solution containing 2.5 weight percent of Na 2 HPO 4 as the liquid phase, was prepared. Seven groups with differing CSD content (0, 5, 10, 20, 30, 40 and 100%) were tested. The injectability of α-TCP increased with increasing proportions of CSD in the mixture; a small addition of CSD powder sharply decreased the setting time of the cement, but further addition caused the setting time of the mixture to increase again. Simultaneously, adding CSD to α-TCP had little effect on the setting temperature. The compressive strength of the cement decreased with increasing content of CSD except in the 5% group, because addition of a small amount of CSD to the cement induced the appearance of fiber-like crystallization; this was confirmed by scanning electron microscopy (SEM). Furthermore, the bone cement mixture had good degradability in simulated body fluid (SBF) when the content of CSD was increased. Key words: Calcium phosphate, calcium sulfate dehydrate, bone cement, injectability, degradability, bonerepair.