Implant fabrication

Nanostructured Hybrid Materials for Bone Implants Fabrication... 

Fig. 17 Syncro-Mate-C implant, a subdermal implant fabricated from the microreservoir dissolution-controlled drug-delivery system, and subcutaneous controlled release of nor-gestomet, a potent synthetic progestin, at constant rate for 20 days. The open ends on the implant do not affect the zero-order in vivo drug release profile. (Adapted from Ref. . )...

Artificial organs and implants fabricated from silicone elastomer have allowed or improved treatment of a variety of human health conditions where no equally effective treatment is otherwise available. 

Carbons can be made in many aUotropic forms crystalline diamond, graphite, noncrystalhne glassy carbon, and quasicrystaUine pyroHtic carbon. Among these, only pyrolitic carbon is widely utilized for implant fabrication it is normally used as a surface coating. It is also possible to coat surfaces with diamond. Although the techniques of coating with diamond have the potential to revolutionize medical device manufacturing, it is not yet commercially available [Park and Lakes, 1992]. 

LTI carbon A silicon alloyed pyrolitic carbon deposited onto a substrate at low temperature with isotropic crystal morphology. It is highly compatible with blood and used for cardiovascular implant fabrication such as artificial heart valve. 

The best known fluorocarbon polymer is polytetrafluoroethylene (PTFE), commonly known as Teflon (DuPont). Other polymers containing fluorine are polytrifluorochloroethylene (PTFCE), polyvinylfluor-ide (PVF), and fluorinated ethylene propylene (FEP). Only PTFE will be discussed here since the others have rather inferior chemical and physical properties and are rarely used for implant fabrication. 

Silicone rubber, developed by Dow Corning company, is one of the few polymers developed for medical use. The repeating unit is dimethyl sUoxane which is polymerized by a condensation polymerization. Low molecular weight polymers have low viscosity and can be cross-linked to make a higher molecular weight, rubber-like material. Medical grade silicone rubbers contain stannous octate as a catalyst and can be mixed with a base polymer at the time of implant fabrication. 

The use of single crystal sapphire or AI2O3 ceramic implants has remained an important component in the dental implant field [Driskell et al., 1973]. Although this material demonstrates excellent biologic compatibility, implants fabricated from AI2O3 have not reached a high degree of popularity in the United... 

An YB, Oh NH, Chun YW, Kim YH, Park JS, Choi KO et al (2005) Surface characteristics of porous titanium implants fabricated by environmental electro-discharge sintering of spherical Ti powders in a vacuum atmosphere. Scripta Mater 53 905-908... 

The ASTM lists four types of CoCr alloys which are recommended for surgical implant apphcations (1) cast CoCrMo alloy (F75), (2) wrought CoCrWNi alloy (F90), (3) wrought CoNiCrMo alloy (F562), and (4) wrought CoNiCrMoWFe alloy (F563). The chemical compositions of each are summarized in Table 38.3. At the present time only two of the four alloys are used extensively in implant fabrications, the castable CoCrMo and the wrought CoNiCrMo alloy. As can be noticed from Table 38.3, the compositions are quite different from each other. 

Attempts to use titanium for implant fabrication dates to the late 1930s. It was found that titanium was tolerated in cat femurs, as was stainless steel and VitaUium (CoCrMo alloy). Titanium s lightness (4.5 g/cm, see Table 38.5) and good mechanochemical properties are salient features for implant application. 

Vanhoestenberghe A, Donaldson N, Lovell N, Suaning G (2008) Hermetic encapsulation of an implantable vision prosthesis - combining implant fabrication philosophies. In IFESS 2008 -from movement to mind, URL http //discovery.ucl.ac.uk/1318417/... 

A third type of silicone implant fabrication is a hybrid of the capsule and matrix-type implants such as microsealed drug delivery system." This system consists of a matrix-type silicone im.plant with microsealed compartments containing drug/steroid dissolved or suspended in a hydrophilic solvent. Addition of solvents in the silicone implants changes the physical structure of the silicone network and affects the solubility and diffusivity of drugs/hormones so that release fluxes of drugs/hormones increase."... 

The objective (the problem to be solved) was to reduce the wear in medical endoprothesis implants fabricated from a titanium alloy. 

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