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Porous low modulus beta-type Ti-Nb alloys for hard tissue implants

Romy Schmidt1, 2*, Matthias Schumacher3*, Ksenia Zhuravleva1*, Matthias Bönisch1, 4, Mariana Calin1*, Jürgen Eckert2, 5, 6*, Michael Gelinsky3* and Annett Gebert1*
  • 1 Leibniz Institute for Solid State and Materials Research, Institute for Complex Materials, Germany
  • 2 Technische Universität Dresden, Institute of Materials Science, Germany
  • 3 Technische Universität Dresden, Centre for Translational Bone, Joint and Soft Tissue Research, Germany
  • 4 Technische Universität Dresden, Institute of Structural Physics, Germany
  • 5 Austrian Academy of Sciences, Erich Schmid Institute of Materials Science, Austria
  • 6 Montanuniversität Leoben, Department Materials Physics, Austria

An important requirement for load-bearing metallic implants is the mechanical compatibility with human bone. That includes high ultimate mechanical strength to withstand the loading conditions in the human body as well as low stiffness matching to that of human bone for the reduction of stress shielding effects. Beta-titanium alloys, e.g. of the Ti-Nb system, are so called “second generation Ti-alloys” and become increasingly important mainly due to their significantly decreased Young’s modulus when compared to established implant materials[1]. A further reduction of stiffness can be achieved by the introduction of porosity into the material. In the present work a powder metallurgical process for the production of fine-grained porous samples by hot compaction of beta-Ti-45Nb powder with NaCl as space holder was developed recently[2]. Different processing routes were evaluated for achieving most suitable mechanical properties in compression. Moreover, the porous alloy bodies are developed as substrates for bioactive and bioresorbable materials that could foster bone bonding and thus, effectively support bone healing processes.

Gas-atomized Ti-45Nb powder (TLS Technik Germany) was employed for the production of microporous samples. The particles had a spherical shape and a particle size distribution of 100 - 250 µm. The samples were either sintered or hot pressed. Furthermore, marco-porous samples were produced using NaCl particles of 125 - 300 µm size as space holder material upon hot pressing. The space holders were afterwards removed by immersion in hot water (80 °C) for 6 hours.

Samples produced with NaCl space holder had a macroporosity of 45 %. In compression, strength values of >200 MPa were determined which are higher than the strength level of human cortical bone. The feasibility of electrodeposition techniques for coating Ti-Nb surfaces with hydroxyapatite is demonstrated. Furthermore, the metallic scaffolds were coated with calcium phosphates (CaP) by the precipitation of CaP from apatite-forming bone cement[3] precursors. Bone cement precursors were suspended in organic solvent and allowed to infiltrate the pores of the metallic scaffolds under vacuum assistance. After drying, setting of the cement into Ca-deficient apatite was performed under humidity at 37 °C. The CaP coating of the metallic surface was studied using SEM. Ca-release from the coated scaffolds as well as coating efficiency were quantified in different media. In summary, this approach resulted in a bioactivation of the surface and thus could increase tissue adherence to the scaffolds. These promising results show the high application potential of macro-porous coated Ti-45Nb bodies as load-bearing metallic scaffolds.

This work was funded by the German Research Society (DFG) as part of the Collaborative Research Centre/Transregio 79 (SFB/ TR 79 – subproject M1, in collaboration with M2).

References:
[1] M. Calin, A. Helth, J. J. Gutierrez, M. Bönisch, V. Brackmann, L. Giebeler, T. Gemming, C. E. Lekka, A. Gebert, and J. Eckert, “Elastic softening of beta-type Ti-Nb alloys by indium ( In ) additions,” J. Mech. Behav. Biomed. Mater., vol. 39, pp. 162–174, 2014.
[2] K. Zhuravleva, A. Chivu, A. Teresiak, S. Scudino, M. Calin, L. Schultz, J. Eckert, and A. Gebert, “Porous low modulus Ti40Nb compacts with electrodeposited hydroxyapatite coating for biomedical applications.,” Mater. Sci. Eng. C. Mater. Biol. Appl., vol. 33, no. 4, pp. 2280–7, May 2013
[3] M. Schumacher, A. Henß, M. Rohnke, and M. Gelinsky, “A novel and easy-to-prepare strontium(II) modified calcium phosphate bone cement with enhanced mechanical properties,” Acta Biomater., vol. 9, no. 7, pp. 7536–7544, 2013

Keywords: Calcium phosphate, 3D scaffold, biofunctionalization

Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.

Presentation Type: Poster

Topic: Metallic biomaterials and alloys

Citation: Schmidt R, Schumacher M, Zhuravleva K, Bönisch M, Calin M, Eckert J, Gelinsky M and Gebert A (2016). Porous low modulus beta-type Ti-Nb alloys for hard tissue implants. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.01654

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Received: 27 Mar 2016; Published Online: 30 Mar 2016.

* Correspondence:
Dr. Romy Schmidt, Leibniz Institute for Solid State and Materials Research, Institute for Complex Materials, Dresden, Germany, Email1
Dr. Matthias Schumacher, Technische Universität Dresden, Centre for Translational Bone, Joint and Soft Tissue Research, Dresden, Germany, Email2
Dr. Ksenia Zhuravleva, Leibniz Institute for Solid State and Materials Research, Institute for Complex Materials, Dresden, Germany, Email3
Dr. Mariana Calin, Leibniz Institute for Solid State and Materials Research, Institute for Complex Materials, Dresden, Germany, Email4
Dr. Jürgen Eckert, Technische Universität Dresden, Institute of Materials Science, Dresden, Germany, Email5
Dr. Michael Gelinsky, Technische Universität Dresden, Centre for Translational Bone, Joint and Soft Tissue Research, Dresden, Germany, Email6
Dr. Annett Gebert, Leibniz Institute for Solid State and Materials Research, Institute for Complex Materials, Dresden, Germany, Email7