Hydroxyapatite-forming capability and mechanical properties of organic-inorganic hybrids and α-tricalcium phosphate porous bodies

We have fabricated α-TCP porous body (pTCP)/hybrid polymer composites consisting of 2-hydroxyethylmethacrylate (HEMA) and 3- methacryloxypropyltrimethoxysilane (MPS) (pTCP/H). The composites showed an apatite-forming capability in a simulated body fluid (SBF) and a higher compressive strength (57 MPa) than pTCP (0.60 MPa). The compressive strength was still lower than human cortical bone (100-230 MPa). Moreover, there was a problem in that some samples formed cracks after soaking in the SBF due to the swelling of the HEMA-MPS polymer. Compared with HEMA, methylmethacrylate (MMA) does not show any swelling after polymerization, and is expected to have a higher mechanical strength than HEMA. We also fabricated a composite from pTCP and a hybrid polymer consisting of MMA and MPS (pTCP/M). The compressive strength of pTCP/M (94 MPa) was higher than that of pTCP/H before soaking in the SBF. The pTCP/M formed a hydroxyapatite layer in the SBF. The pTCP/M did not form cracks, even after soaking in the SBF. The pTCP/M showed both bioactivity and a high compressive strength. This type of composite has potential for novel bone substitute.