Ti-15A1-33Nb (at.%) and T-21A1-29Nb (at.%) Alloys for Biomedical Implant Applications
Erosive bone diseases, such as osteoporosis, periodontitis, rheumatoid arthritis, hypercalcemia of malignancy and aseptic loosening are a growing medical problem which can lead to the need for replacement surgery with bone-replacement materials. Such materials must exhibit several characteristics in order to be successful, including biocompatibility with near-bone hard and soft tissue, a modulus near that for bone to prevent stress shielding, and a tensile and compressive strength and fracture toughness equal to or greater than that of bone. Due to their excellent specific strength and electrochemical corrosion resistance, in addition to exceptional biocompatibility characteristics among metallic biomaterials, titanium and titanium alloys are widely used as structural biomaterials for the replacement of hard tissues in devices such as artificial knee joints and dental implants. In particular, the specific alloy most widely used for implants is Ti-6Al-4V which includes vanadium. However, vanadium is potentially toxic in elemental form and its elastic modulus is significantly greater than that for bone.
Description of Technology
The invention includes two new metal alloys, Ti-15Al-33Nb(at.%) and Ti-21Al-29Nb(at.%), for use in biomedical implant applications. Currently the most commonly used alloy for implants, Ti-6Al-4V, includes vanadium which is potentially toxic in elemental form. Substitution of niobium for vanadium is attractive as this does not result in degradation of several mechanical properties, and the microstructural phases present in Ti-Al-Nb alloys are similar to those in the Ti-V-Al system.
- Eliminates toxicity: Niobium is nontoxic whereas vanadium is toxic in elemental form and may have long term adverse effects on patients.
- Improved elastic modulus: The elastic modulus of implants made from TilSAl-33Nb(at.%) and Ti-21Al-29Nb(at.%) alloys is about half that for stainless steel and Co-Cr-Mo alloys, making it more like bone which must bend without breaking.
- Improved yield strength: The yield strength of TilSAl-33Nb(at.%) and Ti-21Al-29Nb(at.%) alloys range between 800-1200MPa, whereas bone has an ultimate strength of 83-117MPa.
The invention is for use in biomedical implants, most likely as load-bearing implants in both dentistry and bone replacement surgery.
Proof of concept. Initial mechanical property characterization, cytotoxicity, and biocompatibility experiments have been undertaken. (12/7/08)
US 2007/0084530 A1 (filed Oct 18, 2006)
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Michigan State University