Design, selection and characterization of novel glasses and glass-ceramics for use in prosthetic applications

The objective of this work is to design and characterize crystallizable silicate and borosilicate compositions for use in the production of smart, unconventional coatings on bioceramic implants. The concept behind this research is the development of a three-layer implantable system (joint prosthesis) comprising a ceramic substrate, a glass-derived trabecular coating and a glass-ceramic interlayer that joins the other two elements together. The outer porous coating should exhibit bone-like architecture, high mechanical strength and good bioactivity to bond to bone, whereas the interlayer should be chemically stable in biological fluids to avoid detachment between the joined parts. Glasses in the SiO2-Na2O-K2O-CaO-P2O5-B2O3-Al2O3 system have been synthesized by a melting route and thermally treated to obtain glass-ceramic products. A selection of potentially suitable materials for the trabecular coating and interlayer was carried out on the basis of thermal properties and tendency to dissolve in simulated body fluids (SBF) so that the integrity of the final device might be maintained upon implantation. The glass selected for the trabecular coating was processed by sponge replica method to produce glass-ceramic scaffolds, in order to evaluate the material properties and performance in an embodiment plausibly close to the final application. The mechanical properties of the porous glass-ceramic, which mimicked the 3-D pore architecture of cancellous bone, were adequate for load-bearing applications such as joint prostheses. Formation of a surface apatite layer on scaffold struts upon soaking in SBF confirmed the excellent bioactivity of the material, which is a key precondition for in vivo osteointegration.