Mariana Calin

Abstract:

Currently, titanium and its alloys constitute the most favoured implant metallic materials in the field of trauma and orthopaedic surgery. However, despite the high rates of success of Ti-based implant materials, there still are serious problems of safety and long-term durability in the human body, resulting in repeat of surgical operations. For an implant material in contact with bone, both bulk and surface properties of the material have to be considered in order to improve cell–substrate interactions by the surface nano-featuring and to maintain long-term stability of the implant materials. Therefore, much research effort is dedicated to the development of new metastable Ti-based alloys with improved mechanical performance and biological compatibility expressed in low rigidity, high strength, composition of non-toxic elements and optimum surface conditions for osseointegration. Ti-based alloys offer a wide range of adaptable structures for use in different medical applications, especially in orthopedics. In the focus of our studies are the Ti-Nb-based alloys with various metastable structures (beta-type, martensitic, nanostructured, glassy), which are processed by controlled casting and severe plastic deformation as bulk material or by powder metallurgy as porous compacts. In the present paper, we will show that by tailoring specific nanostructures (for example with bimodal grain-size distribution or ultrafine/nano-scaled grains with non-equilibrium grain boundaries) unique combinations of properties can be produced, such as extraordinarily high strength and good ductility combined with high corrosion and wear resistance. The possibility of applying different surface modification techniques for tailoring Ti-Nb implant surfaces at the nano-scale will be presented. The effective applicability of an oxidative H2SO4 treatment for nano-roughening the alloy surface without altering the corrosion resistance will be highlighted. This surface state sensitively determines the cell biological response, e.g. nano-roughening accelerates the adhesion and spreading of human mesenchymal stromal cells and increases the osteogenic differentiation. Another approach is the anodization in F’-containing electrolytes for growth of oxide nanotubes (Ti,Nb)O2. Tube diameter and length are controllable by the applied potential and polarization time and determine critically the cell response. Acknowledgement: Funding from the DFG in the framework of SFB/TR79 and from the EC in the 7. FP MC-ITN VitriMetTech is acknowledged.