Fabrication of chelate-setting cements from hydroxyapatite powders surface-modified with various sodium inositol hexaphosphate concentrations and their mechanical properties

The effect of concentration of sodium inositol hexaphosphate (IP6-Na) on material properties of calcium-phosphate cement (CPC) was investigated. The starting cement powder (IP6-HAp) was prepared by grinding and surfacemodifying hydroxyapatite (HAp) powder in various concentrations of IP6-Na solution. To prepare the IP6-HAp cement paste, the IP6-HAp powder was mixed with water under various powder/liquid ratios (P/L= [g/mL]). Amount of IP6 adsorbed on the surface of HAp powders increased with an increment of IP6-Na concentration, leading to negative surface charge. Dispersion of IP6-HAp powders was improved with an increase of IP6-Na concentration. As for cement fabrication, the IP6-HAp powder with negative charge enabled putty-like cement paste to be prepared at the higher P/L ratio. The compressive strength fabricated from IP6-HAp powders with negative surface charge at -20 mV or lower was higher than that fabricated from IP6-HAp powders with negative surface charge at -10 mV or higher. This improvement of the CS may be due to the increase of packing density.