Hardness evaluation of carbonate apatite cement based on various ratio of precursor

Carbonate Apatite (CO₃Ap) cement is considered as an ideal bone substitute due to its biocompatibility and osteoconductivity. Also, CO₃Ap cement has the chemical composition that closes to natural bone. During cement preparation, precursors play an important role that affects the properties of CO₃Ap cement. Cement hardness is one of the important properties that need to be evaluated before the obtained cement can be applied as a bone substitute. Therefore, the purpose of this study is to determine the effect of precursor ratio of CaCO₃ and CaHPO₄ on the hardness level of CO₃Ap cement. In the present study, the CO₃Ap cement was prepared from CaCO₃ and CaHPO₄. Both Commercial and synthesized CaCO₃ were used. The CO₃Ap cement obtained from commercial CaCO₃ was used as a control group. Synthesized CaCO₃ was obtained from Indonesian natural limestone. Three different CaCO₃:CaHPO₄ ratios, 40:60, 30:70 and 20:80 were mixed with 1 mol/L Na₂HPO₄. Samples were kept at 37^°C with 100% relative humidity for 24 hours then tested using micro Vickers hardness testing machine. The micro Vickers hardness of the control group with CaCO₃:CaHPO₄ ratio of 40:60, 30:70 and 20:80 were 5.09 VHN, 6.34 VHN, and 6.73 VHN, respectively. Meanwhile, the micro Vickers hardness of the CO₃Ap cement obtained from synthesized CaCO₃ were 6.22 VHN, 7.50 VHN, and 10.37 VHN for the CaCO₃:CaHPO₄ ratio of 40:60, 30:70 and 20:80, respectively. The micro Vickers hardness level of CO₃Ap cement precursor ratio from the lowest to the highest was 40:60 < 30:70 < 20:80. In conclusion, the precursor ratio significantly affects the hardness level of the CO₃Ap cement. The hardness level of CO₃Ap cement obtained from synthesized CaCO₃ was higher compared with that obtained from commercial CaCO₃