Poly , implant material

Multiple uses of poly(lactic add), poly(glycolic acid) homopolymers, and poly(lactic-co-glycolic acid) copolymers have been described including sutures, vascular grafts, drug carriers, and scaffolds for tissue engineering (discussed below). This is due in part to the FDA approval of these polymers for use as implantable materials. 

Semi-solid bioerodible implant materials would enable the delivery of soft implants with a needle and syringe. Heller introduced such a material, poly(orthoester) IV, that shows long residence time after subconjunctival administration, an erosion-controlled drug release, and ocular biocompatibility. Depending on the ocular site of injection, the ocular lifetime of the drug ranges from 5 to 6 months. 

Lahann J, Klee D, Hocker H. CVD-polymer-ization of a functionalized poly(p-xylylene). A generally applicable method for the immobilization of drugs on medical implants. Materi-alwiss Werkstofftech 1999 30 763-6. 

Most bioinert rigid polymers are commodity plastics developed for nonmedical applications. Due to their chemical stability and nontoxic nature, many commodity plastics have bwn used for implantable materials. This subsection on rigid polymers is separated into bioinert and bioerodable materials. Table 11.6 contains mechanical property data for bioineit polymers and is roughly ordered by elastic modulus. Polymers such as the nylons and poly(ethylene terephthalate) slowly degrade by hydrolysis of the polymer backbone. However, they are considered bioinert since a significant decrease in properties takes years. 

Poly(ether ether ketone) (PEEK), in various formulations, is found in a wide variety of applications as an alternative biomaterial to ceramic, metal and other polymer implants (such as UHMWPE). These applications include trauma fixation, as well as dental, orthopaedic and spinal implants and, as a result of ongoing research, the uses of PERK as a biomaterial continue to grow (Toth et al. 2006). Research conducted by Morrison et al. (1995) emphasised the biocompatibility of PEEK and its composites. This may mean that the probability of adverse tissue reactions induced by wear debris may be minimised through the use of PEEK as an implant material. 

Some poly [(organo)phosphazene] materials are of interest as biomedical polymers as non-interacting tissue replacement materials. Allcock examined the possibility of poly [(organo) phosphazenes] to be used as coating materials for artificial implants (Allcock et al, 1992). This coating materials should be able to enhance the antibacterial actiwty of the surface of implanted materials. 

By examining the polymeric materials which are currently used in cHnical application it can be seen that while their mechanical properties satisfy requirements, their total compatibility with blood has still not been achieved. Therefore, commercial polymers like polyurethanes, siHcones, polyolefins and poly(vinyl chloride) which are used as short-term implant materials show thrombogenic properties and require the introduction of anticoagulants [26,43]. 

P. Predecki, A Method for Hydron Impregnation of Silicone Rubber, J. Biomed. Mater. Res. 8, 487 (1974). IPNs of silicone rubber and poly(hydroxyethyl methacrylate). Implant materials, particularly arteriovenous shunts. 

Bone and Joint Prostheses.— The present state of the art in the field of joint replacement and complications arising with existing materials has been discussed by various authors. Attention continues to be paid to the mechanical testing of implants and implant materials, particularly with respect to various aspects of the bond strength of the bone/poly(methyl methacrylate) (cement) interface. A stress analysis of the human femur with implanted Charnley prostheses has been carried out. ... 

Polymers are widely used as implant materials because they have physical properties that are similar to those of natural tissues. Examples are long-term and shortterm implants such as blood vessels, heart valves, membranes, mesh prostheses, corneas, tracheal prostheses, dental materials, parts of the nose and ear, knee and hip joints, and others. The synthetic polymers used include polyethylene (PE), particularly ultrahigh molecular weight PE (UHMWPE), poly(ethylene terephthal-ate) (PET), poly(tetrafluoroethylene) (PTFE), polyurethane (PU), and poly(methyl methacrylate) (PMMA). The necessary sterilization before implantation can be performed by y-irradiation, heat (steam), or chemical treatment (ethylene oxide), which should not cause any structural degradation of the polymers. Current challenges in research include the development of biomimetic materials that match both the mechanical and biological properties of their natural counterparts. 

The decrease in resistivity brought about by ion bombardment is accompanied by color chaages in the implanted material, as well as other spectral changes (54). A green color is noted for poly-PTS... 

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