New sintered wollastonite glass-ceramic for biomedical applications

We developed a new bioactive glass-ceramic (GC) based on the CaO-SiO2-MgO-Na2O-Li2O system. Four glass compositions were formulated by a proprietary software (Reformix) and tested by changing mainly the calcium content (from 20 mol% to 40 mol%) and the minor components-alumina, zirconia and zinc oxide. We produced our GCs using the sinter-crystallization process at different temperatures (800-1000 degrees C) and evaluated the effects of compositional changes on the sintering kinetics, microstructure (residual porosity and crystalline phases), hardness, bending strength and bioactivity. We then followed the hydroxycarbonate apatite (HCA) formation in simulated body fluid by Fourier-transform infrared spectroscopy (FTIR), which revealed the onset of HCA formation after approximately 3 days. These GCs are phosphorus and fluorine free, elements that are present in most bioactive glasses, glass-ceramics and ceramics. Our most bioactive GC has a residual porosity of 9 +/- 1%, hardness of 5.5 +/- 0.3 GPa, 4p-bending strength of 98 +/- 7 MPa and is non-cytotoxic. This combination of good bioactivity and mechanical properties (despite its high porosity) suggests that this new GC could be tested for bone graft implants.