Comparison of direct and indirect selective laser sintering of porous apatite mullite glass ceramics

The feasibility of using the layer manufacturing technique of selective laser sintering (SLS) for the fabrication of custom made bioceramic bone implants has been investigated. A castable glass based on the system SiO2-Al2O3-P2O5-CaO-CaF2, which can crystallise to a glass ceramic with fluoroapatite and mullite phases, was used due to its proven bioactivity, good fracture toughness and mechanical strength. Both direct and indirect methods were attempted, the latter adding an acrylic binder to the glass prior to SLS. Porous, three-dimensional parts were successfully produced via both routes. However, the processing window, and coherence of the indirectly sintered components was considerably greater than those produced by the direct routed This is thought to he due to crystallisation only occurring upon post-processing in the indirect samples, therefore allowing an increase in liquid phase sintering. Current indirectly produced parts have a flexural strength similar to that of cancellous boned