Non-decay type fast-setting calcium phosphate cement using chitosan

A non-decay type fast-setting calcium phosphate cement (nd-FSCPC) has been described, which did not decay but set within approximately 5-6 min even when the paste was immersed in serum immediately after mixing, and which forms hydroxyapatite as its end product. nd-FSCPC was produced by adding sodium alginate to the liquid phase of the base cement FSCPC. Sodium alginate forms a water-insoluble gel, and reduces the process of fluid penetration into the paste which is the cause of decay. The aim of this investigation was to confirm the mechanism of the non-decaying behaviour of nd-FSCPC proposed in a previous paper, using another chemical with properties similar to those of sodium alginate. Also, it was intended to further improve both the mechanical properties and tissue response of nd-FSCPC. Chitosan, which also forms a water-insoluble gel in the presence of calcium ions and has been reported to have pharmacologically beneficial effects on osteoconductivity, was added to the liquid phase of the base cement FSCPC. The cement thus prepared showed behaviour similar to that of nd-FSCPC using sodium alginate. The cement paste did not decay but set within approximately 5-6 min even when immersed in serum immediately after mixing. DTS value of the set mass was approximately 3-4 MPa, slightly lower than that of nd-FSCPC using sodium alginate, and no inhibitory effect was observed for the transformation of cement component to apatite within the range used in this investigation (up to 1.5%). Therefore, it was concluded that the mechanism of non-decaying behaviour was, at least in part, reduction of fluid penetration into the cement paste. nd-FSCPC using chitosan showed slightly poorer mechanical properties than that using sodium alginate. However, pharmacological effects such as osteoconductivity could be expected in nd-FSCPC using chitosan. Thus, this cement may be useful as a more sophisticated bioactive cement than nd-FSCPC using sodium alginate.