Medical implant applications

This section deals with how our understauding of the Mg corrosion mechanism can be used to help understand the behaviour of Mg alloys for the other application of growing importance to Mg alloys as biodegradable implants for medical applications. Solutions that elucidate these applicatious tend to form surface films and the corrosion rate decreases with immersion time. 

Witte et al. [79] found that the corrosion rates of AZ91D and LAE442 measured in vivo were orders of magnitude lower than those measured in substitute ocean water prepared according to ASTM-Dl 141-98 [80]. Subsequently, in vitro testing has been carried out in a variety of solutions including (i) Hank s solution, (ii) simulated body fluid (SBF), (iii) artificial plasma (AP), (iv) phosphate buffered saline (PBS) and (v) minimum essential medium (MEM, Invitrogen). 

29 Hydrogen evolution and average corrosion rates for Mg alloys in Hank s solution at 37 °C [81]. 

30 Hydrogen evolution data for four wrought Mg alloys immersed in SBF at 37 °C. Reprinted with permission from Haenzi et al. [82]. 

37 Average corrosion rate for Mg-1.0Mn-1.0Zn in Hank s solution and SBP as a function of immersion time. Reprinted with permission from Yang and Zhang [84]. 

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PLA foams are first utilized in tissue engineering and medical Implant applications, where the high cost of the materials is justified. 

Notice Regarding Long-Term Medical Implant Applications... 

The Dow Chemical Company does not recommend Pellethane elastomers for long-term medical implant applications in humans (more than 30 days). Nor do they recommend the use of Pellethane elastomers for cardiac prosthetic devices regardless of the time period that the device will be wholly or partially implanted in the body. Such applications include, but are not limited to, pacemaker leads and devices, cardiac prosthetic devices such as artificial hearts, heart valves, intra-aortic balloon and control systems, and ventricular bypass assist devices. The company does not recommend any non-medical resin (or film) product for use in any human implant applications. 

PHA have been studied for medical implants applications such as heart valves, vascular tissues, bone tissues, cartilage replacements, nerve conduits, as well as esophagus tissues. 

Halloysite is a biocompatible material but its biodegradability is unclear. Therefore, its usage in medicine may be restricted for dermatological and dental applications or those associated with medical implants [11-14]. 

Two further interesting points of note are that on burning silicones form silica which is an insulator, and thus cables insulated with silicone can function after short term exposure in a fire situation silicones are also physiologically inert and this has led to their use in a wide variety of medical applications, including medical implants. 

UHMWPE possesses a unique combination of mechanical and technological properties and enjoys a variety of special applications based on low friction (solid lubricant), wear resistance (protection of metal surfaces), excellent chemical stability, as well as radiation and neutron resistance. UHMWPE is used in chemical processing, food and beverage industries, foundries, the lumber industry the electrical industry, as medical implants and in mining and mineral processing sewage treatment, and transportation. 

Polyurethanes are part of a very versatile group of materials that find uses in a wide range of applications, both domestic and industrial. Polyurethanes are widely used in many applications such as paints and lacquers, foam mattresses, medical implants, and industrial applications such as rollers, electrical encapsulation, engineering components, shoe soles, seals, and in the mining industry. 

Lactic acid is an important chemical that has wide applications in food, pharmaceutical, cosmetic, and chemical industries. There are increasing interests in production of lactate esters and biodegradable polylactic acid (PLA) from lactic acid. Lactate esters are a relatively new family of solvents with specific properties. They are considered safe and are biodegradable (1). In many situations they can replace toxic solvents. Their functions vary from that of intermediates in chemical reactions to solvents in ink formulations and cleaning applications (2). PLA has been widely used in medical implants, sutures, and drug-delivery systems because of its capacity to dissolve over time (3-5). PLA also can be used in products such as plant pots, disposable diapers, and textile fabrics. 

In consumer applications, titanium is used in golf club heads, jewelry, eyeglass frames, and watches. The Japanese have promoted the use of titanium in roofing and monuments. Other application areas include nuclear-waste storage canisters, pacemaker castings, medical implants, high performance automotive applications, and ordnance armor. 

Molecules interact with the surfaces of solids in almost every environment in the universe. In addition to purely intellectual interest, we customarily justify studying these interactions on technological grounds, heterogeneous catalysis and the fabrication of microchips being the most frequently listed applications. However the field is much more broadly relevant the adsorption and desorption of atoms and molecules on the surfaces of dust grains is very important to molecule formation in the interstellar medium, reactions on the surfaces of ice crystals is important in atmospheric chemistry and reactions at surfaces determine the behaviour of medical implants in our bodies. 

The ability to synthesize carbon nanostmctures, such as fullerenes, carbon nanotubes, nanodiamond, and mesoporous carbon functionalize their surface or assemble them into three-dimensional networks has opened new avenues for material design. Carbon nanostructures possess tunable optical, electrical, or mechanical properties, making them ideal candidates for numerous applications ranging from composite structures and chemical sensors to electronic devices and medical implants. 

A commonly used definition of a biomaterial, endorsed by a consensus of biomaterials experts, is a nonviable material used in a medical device, intended to interact with biological systems. An essential characteristic of biomaterials is biocompatibility, defined as the ability of a material to perform with an appropriate host response in a specific application. The goal of biomaterials science is to create medical implant materials with optimal mechanical performance and stability, as well as optimal biocompatibility. 

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