Hydroxyapatite-forming ability and mechanical properties of organic-inorganic hybrids reinforced by calcium phosphates

The bone-bonding ability, known as bioactivity, of ceramic biomaterials is usually evaluated by the potential for hydroxyapatite (HAp) formation on their surfaces after exposure to a simulated body fluid (SBF) proposed by Kokubo et al. We previously reported that an organic-inorganic hybrid synthesized from 2-hydroxy-ethylmethacrylate and 3-methacryloxypropyltrimethoxysilane showed formation of HAp on its surface in SBF, when calcium ions were incorporated into the hybrid. In the present study, the hybrid was combined with α-tricalcium phosphate porous body or calcium phosphates powder (CPP) consisting of dicalcium phosphate anhydrous and tetracalcium phosphate as the Ca²⁺ sources, to improve the mechanical strength of the hybrid. These composites formed HAp on their surfaces in SBF. The mechanical strength of the hybrid was improved by the reinforcement with calcium phosphates. When CPP was used, the compressive strength of the composite increased after soaking in SBF for one day. The combination of the hybrid and calcium phosphates offers a novel design for bioactive materials.