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 (CaSO4. 2H2O; CSD) powders as the solid phase and an aqueous solution containing 2.5 weight percent of Na2HPO4 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.