Fabrication of novel bioresorbable β-tricalcium phosphate cement on the basis of chelate-setting mechanism of inositol phosphate and its evaluation

We have developed novel bioresorbable β-tricalcium phosphate (β-TCP) cements on the basis of chelate-setting mechanism of inositol phosphate (IP6). The starting cement powders (IP6/β-TCP powders) were prepared by surface-modifying β-TCP particles with IP6. The cement specimen was fabricated by mixing the IP6/β-TCP powder in pure water at desired powder/liquid ratios, and examined the effects of powder properties of the IP6/β-TCP powder on the mechanical strength (compressive strength) of the cement specimens. We focused on the crystalline phase, particle size, specific surface area (SSA), and crystallite size among powder properties. The crystalline phase of resulting cement specimen was β-TCP single phase or mixture of β-TCP and calcium-deficient apatite (CDAp). The β-TCP cement with compressive strength of 13MPa was fabricated from the finelyground β-TCP powders prepared by ball-milling commercially-available β-TCP powder for 4h using zirconia beads with 10mm in diameter. Meanwhile, the β-TCP/CDAp biphasic cement had maximum compressive strength of about 23MPa among the examined cement specimens, it was fabricated from the ball-milled commercially-available β-TCP powder for 3h using zirconia beads with 10mm in diameter, and then for 3h using zirconia beads with 2mm in diameter. In order to make the determining factors of the compressive strength clear, we examined the relationship between powder properties (particle size, SSA and crystallite size) and compressive strength. The strength of the IP6/β-TCP cement was not dependent on the particle size of the IP6/β-TCP powder; meanwhile, the strength was enhanced with increasing SSA and decreasing crystallite size. Thus, the IP6/β-TCP powder with higher SSA and smaller crystallite size may be useful in the fabrication of chelate-setting β-TCP cement with enhanced mechanical properties.