Basic properties of carbonate apatite cement consisting of vaterite and dicalcium phosphate anhydrous

The aim of the present study is to fabricate bone cement that could transform to carbonate apatite (CO₃Ap) completely at body temperature. The powder phase of vaterite and dicalcium phosphate anhydrous (DCPA) was mixed with 0.8 mol/L of NaH₂PO₄, Na ₂HPO₄, and Na₃PO₄ aqueous solution, respectively, with liquid to powder ratio (L/P ratio) of 0.45, 0.55, and 0.65. The paste was packed into split stainless steel mold, covered with the glass slide and kept at 37°C and 100% relative humidity for up to 96 hours (h). XRD analysis revealed that the cement became pure CO₃Ap within 24 h for Na₃PO₄, 72 h for Na₂HPO₄, and 96 h for NaH₂PO₄, respectively. FT-IR results showed that all of the obtained specimens could be assigned to B-type CO₃Ap. CHN analysis showed the carbonate content of the specimen were 10.4 ± 0.3% for NaH₂PO₄, 11.3 ± 0.7% for Na₂HPO ₄, and 11.8 ± 0.4% for Na₃PO₄, respectively. Diametral tensile strength of the set CO₃Ap cement was 1.95 ± 0.42 MPa for NaH₂PO₄, 2.53 ± 0.53 MPa for Na₂HPO₄, and 3.45 ± 1.53 MPa for Na ₃PO₄, respectively. The set CO₃Ap cement had low crystallinity similar to bone apatite since it was synthesized at body temperature. We concluded, therefore, that CO₃Ap cement prepared from the present method has higher possibility to be used as an ideal bone replacement.