Biocompatibility Study of Zirconium-Based Bulk Metallic Glasses for Orthopedic Applications
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TRODUCTION
METALLIC materials play an important role in the biomedical field. The significant impact is evident from the extensive list of clinical uses of metallic materials, examples of which include artificial joints, dental implants, maxillofacial devices, stents, artificial hearts, neural prostheses, and more. Particularly for orthopedic applications, metallic materials have been favored due to their excellent mechanical properties, such as strength and fracture toughness. The most commonly used metallic biomaterials for orthopedics include stainless steels, titanium and its alloys, and cobalt-chromium alloys.[1] Despite great progress over the years, these materials suffer from several drawbacks, a major one being causing stress shielding. Stress shielding is a phenomenon related to the mismatch of Young’s moduli of the metallic biomaterial and the surrounding bone.[2] As shown in Table I, the Young’s modulus of a natural bone is typically 3 to 50 GPa, at least half or less compared to the currently used bulk metallic biomaterials.[3] As a result, the majority of the mechanical load is assumed by the high strength metallic implant in the repair region, shielding the surrounding bone from experiencing the stress. This trend eventually causes the bone resorption and complications at the implant/tissue WEI HE, Assistant Professor, Department of Materials Science and Engineering and Department of Mechanical, Aerospace, and Biomedical Engineering, and ANDREW CHUANG and ZHENG CAO, Graduate Students, and PETER K. LIAW, Professor, Department of Materials Science and Engineering, are with the University of Tennessee, Knoxville, TN 37996. Contact e-mail: [email protected] This article is based on a presentation given in the symposium ‘‘Bulk Metallic Glasses VI,’’ which occurred during the TMS Annual Meeting, February 15–19, 2009, in San Francisco, CA, under the auspices of TMS, the TMS Structural Materials Division, TMS/ASM: Mechanical Behavior of Materials Committee. Article published online January 30, 2010 1726—VOLUME 41A, JULY 2010
interface.[4] Therefore, it is critical to maintain the Young’s modulus of the implant material close to that of bone for the desirable long-term clinical performance. Recent advancement in amorphous alloys offers a potential alternate to overcome the stress shielding effect. The amorphous alloys, commonly known as bulk metallic glasses (BMGs), have garnered intense research interest in the materials community due to their remarkable properties. These properties include extremely high elastic strains (~2 pct) in comparison with the common crystalline metallic alloys (
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