Fabrication of chelate-setting cement from hydroxyapatite powder prepared by simultaneously grinding and surface-modifying with sodium inositol hexaphosphate and their material properties

We have previously developed hydroxyapatite (HAp) cement based on the chelate-setting mechanism of sodium inositol hexaphosphate (IP6-Na). In the present study, the effect of the IP6-Na concentration on material properties, such as compressive strength, setting time, consistency, and anti-washout capability, of the chelate-setting hydroxyapatite cement was investigated with the aim to develop paste-like artificial bone with anti-washout capability. Starting powders for cement fabrication (IP6-HAp powder) were prepared by simultaneous grinding and surface-modification of the HAp powder in various concentrations (020000 ppm) of IP6-Na solution. The amount of IP6 adsorbed on the surface of the HAp powders increased with the IP6-Na concentration and resulted in a negative charge on the powder surface. Dispersion of the IP6-HAp powder was improved with increasing IP6-Na concentration. A workable cement paste was prepared from the negatively charged IP6-HAp powder (<-20 mV) at a higher powder/liquid ratio, regardless of the low water content. The compressive strength of the resulting cement specimens increased from 1.4 to 8.3MPa with an increase of the relative density. HAp powders surface-modified with 5000 to 10000 ppm IP6-Na are effective for fabrication of IP6-HAp cements with enhanced material properties. In particular, surfacemodification with 5000 and 10000 ppm IP6-Na improved the handling feasibility of the cement paste. IP6-HAp cement fabricated by controlling the IP6-Na concentration is promising as an injectable artificial bone for minimally-invasive treatment.