Implant material

The adhesion molecules (i.e., gelatin, fibronectin, coUagen, Min3) were covalently coupled to an artificial blood vessel made from PTEE. Due to unspecific adhesion of fibrin and collagen to the implant surfaces, thrombus formation and occlusion may occur in clinical use. To overcome this problem, the concept of EC cultivation on modified implant material was developed to mimic the physiological surface of blood vessels [36]. The expiration of these ceU layers strictly depends on the cell-surface interaction, which can be improved by modifying the graft surface with adhesion molecules. 

Commercially available PTFE was used for the investigations (Merck). We developed the method and the parameters (acids, concentration, ratio, time) for the wet-chemical modification of PTFE on the basis of PTFE film material (thickness 0.1 mm) punched in 12 mm disks. Then the results from the PTFE film model were transferred and adjusted to medical grade vascular grafts (B. Braun AG see Fig. 11.1). 

---

Sittig C, Flahner G, Marti A, Textor M, Spenoer N D and Flauert R 1999 The implant material, Ti6AI7Nb surfaoe miorostruoture, oomposition, and properties J. Mater. Sc/. 10 191... 

Chaimelling only requires a goniometer to inelude the effeet in the battery of MeV ion beam analysis teelmiques. It is not as eonnnonly used as tire eonventional baekseattering measurements beeause the lattiee loeation of implanted atoms and the aimealing eharaeteristies of ion implanted materials is now reasonably well established [18]. Chaimelling is used to analyse epitaxial layers, but even then transmission eleetron mieroseopy is used to eharaeterize the defeets. 

Over time a large variety of materials have been used, including ivory, stainless steel, chromium—cobalt, and ceramics for the acetabular component. None proved sufficient. The implant material composition must provide a smooth surface for joint articulation, withstand hip joint stresses from normal loads, and the substance must disperse stress evenly to the cement and surrounding bone. 

The concept of using biodegradable materials for implants which serve a temporary function is a relatively new one. This concept has gained acceptance as it has been realized that an implanted material does not have to be inert, but can be degraded and/or metabolized in vivo once its function has been accompHshed (12). Resorbable polymers have been utilized successfully in the manufacture of sutures, small bone fixation devices (13), and dmg dehvery systems (qv) (14). 

D. E. Williams, in Syrett and Acharya, eds.. Corrosion and Degradation of Implant Materials, ASTM STP684, American Society for Testing and Materials, Philadelphia, Pa., 1979, pp. 61—75. 

Requirements. Requirements for dental implant materials are the same as those for orthopedic uses. The first requirement is that the material used ia the implant must be biocompatible and not cause any adverse reaction ia the body. The material must be able to withstand the environment of the body, and not degrade and be unable to perform the iatended function. 

It is widely appreciated that the deterioration of metal and plastic implant materials within the body is one of the most important aspects of implant surgery. This particular application of materials places an almost unique demand on the resistance to deterioration. The reasons are basically twofold, for not only may the environmental effects alter the structure and properties of the material, which may itself affect the function of the implant and hence the well-being of the patient, but also the by-products of any structural change may have harmful effects on the patient... 

Greene, N. D., Corrosion of Surgical Implant Alloys A Few Basic Ideas , in Corrosion and Degradation of Implant Materials, Second Symposium, (Eds) A. C. Fraker and C. D. Griflin, 5-10 ASTM Publication STP 859, Philadelphia (1985)... 

Hughes, A. N., Jordan, B. A. and Orman, S., The Corrosion Fatigue Properties of Surgical Implant Materials. Third Progress Report — May 1973 , Engineering in Medicine, 7, 135-141 (1978)... 

Revie, R. W. and Greene, N. D., Corrosion Behaviour of Surgical Implant Materials 1 Effects of Sterilisation , Corrosion Science, 9, 755-761 (1969)... 

Syrett, B. C. and Wing, S. S., Pitting Resistance of New and Conventional Orthopaedic Implant Materials —Effect of Metallurgical Condition , Corrosion, 34A, 138-145 (1978)... 

Sury, P., Corrosion Behaviour of Case and Forged Implant Materials for Artificial Joints, Particularly with Respect to Compound Designs. Research and Development Department, Sulzer Brothers Ltd., CH-8401, Winterthur, Switzerland. 

Body fluids and tissues Tantalum is a very stable passive metal and completely inert to body fluids and tissues. Bone and tissue do not recede from tantalum, which makes it attractive as an implant material for the human body" . 

Principles In this process, ions of almost any material can be implanted into a substrate to alter its surface properties, such as resistance to wear, corrosion, and oxidation, as well as many others. The implanted material is not... 

Properties of the deposit The changes in surface properties of implanted materials which can be achieved are very considerable. Physical and chemical properties can be widely varied to produce special characteristics, some of which cannot be obtained in any other way. 

Isotropic carbon is obtained by the pyrolysis of a hydrocarbon, usually methane, at high temperature (1200-1500°C) in a fluidized bed on a graphite substrate.Under these conditions, a turbostratic structure is obtained which is characterized by very little ordering and an essentially random orientation of small crystallites. In contrast to graphite which is highly anisotropic, such a structure has isotropic properties (see Ch. 7). Isotropic carbon is completely inert biologically. Its properties are compared to alumina, another common implant material, in Table 17.8. Notable is its high strain to failure. 

While the mechanical performance of artificial materials in the human body can be predicted with some rehabihty, forecasting their biological performance is difficnlt. The problem of interactions at surfaces has already been mentioned. Research frontiers also include developing ways to simulate in vivo processes in vitro and extending the power and apphcability of such simulations to allow for better prediction of the performance of biomedical materials and devices in the patient. Fundamental information on the correlation between the in vivo and in vitro responses is limited. Chemical engineers might also make contribntions to the problem of noninvasive monitoring of implanted materials. 

Oscillating intracardiac mass on valve or supporting structures, in the path of regurgitant, or on implanted material in the absence of an alternative anatomic explanation, or Abscess, or... 

In consideration of the clinical importance of being able to visualize any implant material within the body, radio-opaque hydrogels for NPR have been formulated [69]. Copolymers of iodobenzoyl-oxo-ethyl methacrylate (4IEMA) and hydrophilic PVP or hydroxylethyl methacrylate (HEMA) exhibit appropriate swelling characteristics, viscoelastic mechanical properties, and excellent cytocompatibility [69]. Moreover, inclusion of the covalently attached iodine molecules allowed for hydrogel visualization via X-ray in a porcine cadaveric spine model [69],... 

---