Abstract
Introduction
Because of its high strength and allowance for bone integration, Ti-6Al-4V is the most commonly used material for load bearing bone implants. Compared to conventional production methods, 3D printing Ti-6Al-4V introduces advantages as (near-) net-shape manufacturing of complex geometries, and optimization of utilization rate of the material. However, as result of the additively production procedure, microstructure and surface properties differ from those manufactured using conventional techniques. Therefore, the resulting mechanical properties and biocompatibility of the 3D printed Ti-6Al-4V are investigated in this study. First, it was aimed to reveal the tensile properties of the material and verify if these depend on build orientation. Second, it was determined which post process method provides the best osteoconductivity.
Materials and methods
Tensile specimens were designed and 3D printed using Selective Laser Melting (SLM) technique. Subsequently, specimens were heat treated and tensile properties were determined as described in ASTM E 8M-04. Cell culture discs were manufactured using the same production method. The influence of two different surface treatments (sand-blasting versus polishing) on osteoconductivity was analysed by a 30 day in vitro 2D culture of bovine Bone Marrow Stromal Cells (bBMSCs). Cultures were checked for morphology, collagen production was monitored, ALP activity was revealed, and matrix mineralization was quantified.
Results
Except for maximum elongation, all tensile parameters were found to be comparable, or even superior to standards for annealed cast respectively forged Ti-6Al-4V. Additionally, results suggest that build orientation does not induce significant variations in tensile properties. The results of the 30 day cell culture suggested that sand-blasting, compared to polishing, resulted in a rougher surface thus ensuring better osteoconductivity. Additionally, none of the cell culture experiments gave any signal of an adverse effect of 3D printed material on cell behaviour or viability.
Conclusion
This research study focused on tensile properties of 3D printed Ti-6Al-4V as a quick method to detect possible material anomalies and reveal essential material properties. Although acceptable tensile properties were found, further research is recommend to better understand the long-term behaviour of 3D printed Ti-6Al-4V. Surface sand-blasting showed to be a proper post-treatment to ensure an osteoconductive surface. Future research will analyse 3D scaffold structures and include histological analysis as well. In general, the results suggest that both mechanical properties and biocompatibility of 3D printed Ti-6Al-4V are excellent for its role as bone implant.
