Preparation and study of in vitro bioactivity of PMMA-co-EHA composites filled with a Ca3(PO4)2-SiO2-MgO glass

The nature of the orthopaedic implant surface affects the interaction with cells and subsequent bone formation. The bone/cement interface in cement-held prostheses is considered to be the main cause of fracture leading to implant revision. It is thought that the introduction of a bioactive phase, such as bioglass, in the cement may permit a more stable interface by encouraging direct bone apposition rather then encapsulation of the implant by fibrous tissue. In this work new poly(methylmethacrylate) (PMMA) based composites filled with 0, 30, 40 and 50 (wt.%) of a Ca3(PO4)2-SiO2-MgO glass, were processed. The prepared composites consist of a poly(methylmethacrylate)-co-(ethylhexylacrylate) (PMMA-co-EHA) matrix filled with a glass (G7), with nominal composition 33.26CaO, 28.07P2O5, 23.03SiO2, 15.64MgO (wt.%). The in vitro bioactivity of the composites was assessed by determining the changes in surface morphology and composition, by X-ray diffraction (XRD) and scanning electron microscopy coupled with X-ray energy dispersive spectroscopy (SEM-EDS), after soaking in a simulated body fluid (SBF) for periods of up to 21 days at 37 °C. Inductively coupled plasma (ICP) was used to assess the evolution of ionic concentrations in the SBF solution. The results obtained confirmed the growth of a hydroxyapatite (HA)-like layer on the surface of the prepared composites. As expected, HA layer formation was faster for composites prepared with higher glass content.