Non-decay type fast-setting calcium phosphate cement: composite with sodium alginate

Non-decay type fast-setting calcium phosphate cement (nd-FSCPC) was prepared by introducing sodium alginate (0-2.0 wt%) into the liquid phase of FSCPC. nd-FSCPC was stable even when the cement paste was immersed in distilled water immediately after mixing, whereas conventional FSCPC (c-FSCPC) decayed completely within 1 min upon immersion. The setting time of the cement, approximately 5 min, was not dependent on the presence of sodium alginate. In contrast, the introduction of sodium alginate into conventional CPC, i.e. CPC without neutral phosphate in the liquid phase, resulted in no setting when the amount of sodium alginate introduced was more than 1 wt%. Powder X-ray diffraction analysis revealed no significant difference for the conversion of cement to apatite for any concentrations of sodium alginate studied (0-2.0 wt%). The mechanical strength of the cement increased rapidly with the addition of sodium alginate up to 0.8 wt% when the cement paste was immersed and kept in distilled water at 37 degrees C, whereas further addition of sodium alginate decreased the mechanical strength. The results obtained in this investigation, taken together with sodium alginate's known excellent biocompatibility and absorption behaviour, indicate that the use of sodium alginate composite FSCPC as nd-FSCPC should be of value in orthodontics and oral and maxillofacial surgery where the cement is exposed to blood.