Titane Bêta Biocompatible Adaptatif – TIBBIA

In implantology, biointegration of the implant is known to be a major issue for the long term clinical success. This biointegration is conditioned by different kinds or parameters such as the chemical nature and the mechanical compatibility of the material regarding the bone/implant interface. Currently, osseointegrated implants are made of Cr-Co alloys, Stainless steel (316L), pure Titanium or conventional TA6V titanium alloys.Titanium and its alloys have emerged as the most promising candidates for the realization of highly bio-compatible and high performance implant materials. However, it is recognized, that in the long-term effect of these implants may be associated with adverse local and remote tissue reactivities (inflammatory reactions) since the use of alloying elements such as Aluminium or Vanadium is still highly questionable. As a consequence there is an increasing need for improved materials displaying: - Superior chemical biocompatibility to ensure the long term inertness of the osseointegrated implant - High specific resistance associated with reduced elastic mismatch between the implant and the surrounding bone, to trigger the load transfer regime at the bone implant/ interface and avoid the so called 'stress shielding' phenomenon. In the frame of this project, it is proposed to develop a new set of beta metastable titanium alloys, composed of biocompatible chemical elements such as Ti, Zr, Ta and Nb, and displaying an improved mechanical compatibility with tissues. (i) Chemical formulation of the (Ti-Ta-Nb-Zr) alloys should result in materials with reduced intrinsic (enthalpic) elastic modulus and well adapted to implantology field. (ii) Additional compositional modifications based on the Morigana prediction model will give possibilities to provide alloys displaying mechanical instability and superelastic properties. This will lead to possible Ni-free alternatives to Ni-Ti alloys for medical application such as stents or orthodontic wires. The originality and the novelty of the project are to take advantage of a double effect. The (Ti-Ta-Nb-Zr) based alloys have already been shown to display a unique combination of low intrinsic modulus keeping mechanical resistance at a high level compared to pure titanium. Careful adjustment of the chemical composition will provide an additional benefit since, in this particular class of materials, the beta matrix can display a mechanical instability leading to a reversible stress induced phase transformation alpha ''. This reversible phase transformation results in a remarkable superelestic effect leading to a drastic decrease of the apparent Young modulus. As a consequence, it will be possible to reduce the elastic mismatch between the implant and the surrounding tissues using the remarkable elastic properties of these alloys. The work will deal with alloys formulation, synthesis, structural characterization and optimization of the associated mechanical properties regarding superelastic properties. The project will provide well defined protocols concerning the elaboration way and the subsequent thermomechanical treatments as a technological input for industrial development in the field of medical devices. This project has been organised on the basis of the complementary expertise of 4 academic partners and is supported by 2 industrials partners to ensure a technological transfer of the developed systems in the growing field of medical devices. It is an ideal way to provide a internationally competitive consortium, gathering complementary forces of metallurgists and increasing involvement of two French companies in the biomedical field.