Influence of pH and ion components in the liquid phase on the setting reaction of carbonate apatite granules

Carbonate apatite (CO₃Ap) is an inorganic component of bone and replaces by natural bone after implantation into the bone defect. Because of this unique characteristic, CO₃Ap granules have been used in the dental field. However, washing out of granules from the bone defect area is an issue. The aim of this study was to set CO₃Ap granules by mixing CO₃Ap granules with acidic phosphate solutions and evaluate the influence of the pH and ion components of the solutions. When Na⁺ was the counter ion, the amount of precipitated dicalcium phosphate dihydrate (DCPD) was small and the setting ability disappeared with increasing pH of the solutions. Alternatively, when the counter ion was Ca²⁺, the amount of precipitated DCPD was high and the setting ability was observed even at high pH. These results suggest the presence of Ca²⁺ in the acidic phosphate solution is a key for fabricating CO₃Ap granular cement.