Substrate bioceramic

Hackley, V. A., Polyelectrolyte adsorption in bioceramic systems Hydroxyapatite as a substrate material, inPolymers in Particulate Systems, Hackley, V. A., Somasundaran, P., and Lewis, J. A., eds., Marcel Dekker, New York, 2001, p. 295. 

Table 1 Uses of Alumina Solid alumina Furnace components Catalyst substrates Electronics substrates Electrical insulators Cutting tools Bearings Spark Plugs Arc lamp tubes Laser hosts Gem stones Alumina powders Abrasives Catalyst pellets Alumina coatings Oxidation protection of aluminum and aluminum alloys Capacitors Transisitors Bioceramics Alumina fibers Thermal insulators Fire retardation Alumina as a component of...

Work performed on depositing bioceramic materials, in particular, hydroxyapatite by CGDS is still few and far between. This is mainly caused by the fact that hydroxyapatite in its pure form cannot be sprayed by CGDS but requires the presence of a ductile, that is metallic matrix that provides adhesion to the substrate by deformation during impact. 

Bioceramic coatings are often used on metallic substrates in which the fracture toughness of the metal is combined with the ability of the coating to present a bioactive surface to the surrounding tissue. The use of a bioceramic coating on a metal implant can lead to earlier stabilization of the implant in the surrounding bone and extend the functional life of the prosthesis. Under the proper conditions a cementless prosthesis should remain functional longer than a cemented device in which stability is threatened by fracture of the bone cement. 

FTIR spectroscopy has proven to be particularly useful in gaining an understanding of the biocompatibility phenomenon. It is believed [746, 841, 856, 857] that protein adsorption is the initial step in the interaction of blood with implanted biomaterials, followed by adhesion of cells and subsequent tissue attachment. This implies that the substrate surface characteristics influence the process, which was confirmed by ATR studies of albumin adsorption on calcium phosphate bioceramics and titanium [763] and segmented polyurethane [764], albumin and fibrinogen on acetylated and unmodified cellulose [765, 766], poly(acrylic acid)-mucin bioadhesion [767], polyurethane-blood contact surfaces [768], and other proteins on poly(ester)urethane [769], polystyrene [767, 771] and poly(octadecyl methacrylate) [771] and by IRRAS study of adsorption of proteins on Cu [858]. Another branch of IR spectroscopic studies of protein adsorption relates to microbial adhesion (Section 7.8.3). 

Calcium-idiosphate-based bioceramics have also been used as coatings on dense implants and porous surface layers to accelerate and enhance fixation of a substrate biomaterial to tissue (Kohn and Ducheyne, 1992 Cook et al 1992 Ducheyne et al., 1980 Oonishi et al., 1994). Results of these smdies vary with respect to bond strength, solubility, and overall in vivo function, suggesting a window of material variability in parallel with a window of biologic variability (Kohn and Ducheyne, 1992). 

Unfortunately, the metallic biomaterials do not sufficiently replicate the surface of the replaced bone and, as a consequence, failures of implants do occur due to insufficient bonding with adjacent bone. Hence, surface treatments are often required for better biocompatibihty and osteointegration. Bioceramic coatings are widely used on medical metalhc implants to modify the surface so that the implants possess the bulk properties of the substrate, i.e. the good mechanical performances of metals and the bioactive properties of bioceramics. 

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