tailieunhanh - Biomaterials

Metals are used as biomaterials due to their excellent electrical and thermal conductivity and mechanical properties. Since some electrons are independent in metals, they can quickly transfer an electric charge and thermal energy. The mobile free electrons act as the binding force to hold the positive metal ions together. This attraction is strong, as evidenced by the closely packed atomic arrangement resulting in high specific gravity and high melting points of most metals. Since the metallic bond is essentially nondirectional, the position of the metal ions can be altered without destroying the crystal structure resulting in a plastically deformable solid | 1 Metallic Biomaterials Joon B. Park University of Iowa Young Kon Kim Inje University Introduction. 1-1 Stainless Steels. 1-2 CoCr Alloys . 1-4 Ti Alloys. 1-6 Pure Ti and Ti6Al4V TiNi Alloys Dental Metals . 1-12 Other Metals . 1-12 Corrosion of Metallic Implants. 1-13 Electrochemical Aspects Pourbaix Diagrams in Corrosion Rate of Corrosion and Polarization Curves Corrosion of Available Metals Stress Corrosion Cracking Manufacturing of Implants. 1-18 Stainless Steels Co-Cr Alloys Ti and Its Alloys Defining Terms. 1-19 References . 1-19 Further Reading. 1-21 Introduction Metals are used as biomaterials due to their excellent electrical and thermal conductivity and mechanical properties. Since some electrons are independent in metals they can quickly transfer an electric charge and thermal energy. The mobile free electrons act as the binding force to hold the positive metal ions together. This attraction is strong as evidenced by the closely packed atomic arrangement resulting in high specific gravity and high melting points of most metals. Since the metallic bond is essentially nondirectional the position of the metal ions can be altered without destroying the crystal structure resulting in a plastically deformable solid. Some metals are used as passive substitutes for hard tissue replacement such as total hip and knee joints for fracture healing aids as bone plates and screws spinal fixation devices and dental implants because of their excellent mechanical properties and corrosion resistance. Some metallic alloys are used for more active roles in devices such as vascular stents catheter guide wires orthodontic archwires and cochlea implants. The first metal alloy developed specifically for human use was the vanadium steel which was used to manufacture bone fracture plates Sherman plates and screws. Most metals such as iron Fe chromium Cr cobalt Co nickel Ni titanium Ti tantalum Ta niobium Nb molybdenum Mo and tungsten W that were