Institute of Fundamental Technological Research

In recent decades, several novel Ti alloys have been developed in order to produce improved alternatives to the conventional alloys used in the biomedical industry such as commercially pure titanium or dual phase (alpha and beta) Ti alloys. Gum Metal with the non-toxic composition Ti–36Nb–2Ta–3Zr–0.3O (wt. %) is a relatively new alloy which belongs to the group of metastable beta Ti alloys. In this work, Gum Metal has been assessed in terms of its mechanical properties, corrosion resistance and cell culture response. The performance of Gum Metal was contrasted with that of Ti–6Al–4V ELI (extra-low interstitial) which is commonly used as a material for implants. The advantageous mechanical characteristics of Gum Metal, e.g. a relatively low Young's modulus (below 70 GPa), high strength (over 1000 MPa) and a large range of reversible deformation, that are important in the context of potential implant applications, were confirmed. Moreover, the results of short- and long-term electrochemical characterization of Gum Metal showed high corrosion resistance in Ringer's solution with varied pH. The corrosion resistance of Gum Metal was best in a weak acid environment. Potentiodynamic polarization studies revealed that Gum Metal is significantly less susceptible to pitting corrosion compared to Ti–6Al–4V ELI. The oxide layer on the Gum Metal surface was stable up to 8.5 V. Prior to cell culture, the surface conditions of the samples, such as nanohardness, roughness and chemical composition, were analyzed. Evaluation of the in vitro biocompatibility of the alloys was performed by cell attachment and spreading analysis after incubation for 48 h. Increased in vitro MC3T3-E1 osteoblast viability and proliferation on the Gum Metal samples was observed. Gum Metal presented excellent properties making it a suitable candidate for biomedical applications.

Gum Metal, mechanical behavior, in vitro corrosion resistance, in vitro biocompatibility, implant applications

In this work, mechanical properties of a β-Ti alloy Gum Metal (Ti–23Nb–0.7Ta–2.0Zr–1.2O at.%, free of cytotoxic content), which was fabricated at Toyota Central Research&Development Laboratories, Inc., were investigated. It was confirmed that Gum Metal is characterized by a low Young's modulus (around 60 GPa), high strength (over 1000 MPa) and a large range of reversible deformation, which are important features in the context of potential implant applications. Moreover, a comprehensive assessment of biocompatibility was realized. Properties of Gum Metal were contrasted with those of Ti-6Al-4V (ELI) which was taken as reference. Surface conditions, such as topography, roughness and structural composition, were analyzed. Evaluation of biocompatibility for the alloys was performed by cell attachment and spreading analysis after predefined cell culture periods. Gum Metal presented excellent properties, what makes it a goodcandidate for implant applications.

Gum Metal, titanium alloy, biocompatibility, implant applications