Incorporation Of Carbonate, Sodium, And Potassium In Bulk Hydroxyapatite Materials

Objectives: Objective: To determine the relationships between the amount of a nCaP component initially present in the calcium phosphate cement powder and the amount incorporated into the hydroxyapatite product.
Methods: Methods: Bulk hydroxyapatite materials were prepared at ambient temperatures using a calcium phosphate cement system previously developed for bone defect repair applications. These materials contain targeted amounts of non-calcium phosphate (nCaP) but biologically relevant components such as carbonate, sodium, and potassium. The cement uses tetracalcium and dicalcium phosphates as starting materials and forms nano-sized hydroxyapatite crystals as the only product. When nCaP components are included in the cement ingredients, these components are incorporated into the apatite crystal structure of the product. In the present study, various amounts of NaHCO₃, KHCO₃, and NH₄HCO₃ or combinations thereof were included in the cement powder, and an ammonium phosphate solution was used as the cement liquid. Hardened cement samples were incubated in a NH₄NO₃ solution for 24h and then dried in air before being characterized by XRD, FTIR and analyzed for carbonate, sodium and potassium contents.
Results: Results: (1) XRD results showed that in all instances a low crystalline apatite was the only product formed, (2) For each nCaP component, there was a linear relationship (R² = 0.982 to 0.999) between the amounts of the component initially present in the cement powder and that incorporated into the apatite product. (3) FTIR analysis suggests that the carbonate was type-b carbonate, (4) of the three nCaP components studied, potassium was the most difficult element to be incorporated as indicated by the smallest slope in the linear relationship.
Conclusions: Conclusion: The result suggests that this method can be used to prepare bulk apatite materials that have nCaP contents like those present in the biological minerals in enamel, dentin, and bone.