Implant material bone tissue

The term biocompatibility is defined as the ability of a material to perform with an appropriate host response in a specific situation" (Williams 2008). A biocompatible material can be inert, where it would not induce a host immune response and have little or no toxic properties. A biocompatible material can also be bioactive, initiating a controlled physiological response. For porous silicon, bioactive properties were initially suggested based on the observation that hydroxyapatite (HA) crystals grow on microporous silicon films. HA has implications for bone tissue implants and bone tissue engineering (Canham 1995). An extension of this work showed that an applied cathodic current was able to further promote calcification on the surface (Canham et al. 1996). More recently, Moxon et al. showed another example of bioactive porous silicon where the material promoted neuron viability when inserted into rat brains as a potential neuronal biosensor, whereas planar silicon showed significantly fewer viable neurons surrounding the implant site (Moxon et al. 2007). 

Phase and chemical composition of bioactive materials is selected so as to ensure that implant surface adjacent to tissue or body fluids constitutes an intermediate layer which connects an implant with bone tissue. A variety of materials which fulfil such criteria have been developed in recent years. The most frequently used bioceramics, due to their high mechanical, corrosion and wear resistance as well as their non-toxicity and biocompatibility, include oxides AI2O3 (whose use for medicine is dated back to the thirties of the past century), Zr02 and calcium phosphates (Tab. 1, 2). 

Drug encapsulation Functional drug carriers Drug discovery Implantable materials Tissue repair and replacment Implant coatings Tissue regeneration scaffolds Structural implant materials Bone repair... 

The materials used in a total joint replacement ate designed to enable the joint to function normally. The artificial components ate generally composed of a metal piece that fits closely into bone tissue. The metals ate varied and include stainless steel or alloys of cobalt, chrome, and titanium. The plastic material used in implants is a polyethylene that is extremely durable and wear-resistant. Also, a bone cement, a methacrylate, is often used to anchor the artificial joint materials into the bone. Cementiess joint replacements have mote tecentiy been developed. In these replacements, the prosthesis and the bone ate made to fit together without the need for bone cement. The implants ate press-fit into the bone. 

Hydroxyapatite (HA) coating on the surface of the hip stem and the acetabular cup is the most recent advancement in artificial hip joint implant technology. This substance is a form of calcium phosphate, which is sprayed onto the hip implant. It is a material found in combination with calcium carbonate in bone tissue, and bones can easily adapt to it. When bone tissue does grow into HA, the tissue then fixes the hip joint implant permanently in position. These HA coatings are only used in press-fit, noncemented implants. 

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" . 

With a bio-inert material, like aluminium oxide, the tissue makes direct contact with the implant material after some time. When a bio-tolerant material like bone cement is introduced, new bone tissue is formed at some distance from the implant. A layer of connective tissue separates the implant from the bone tissue. In the case of a bio-active material, like for instance hydroxyapaptite, new tissue penetrates the implant. In due course the original separation between the implant and tissue disappears. In this way the implant is as it were integrated into the tissue. 

As well as being used as a scaffold for tissue engineering, Hutchens et al. [64] described the creation of a calcium-deficient hydroxyapatite, the main mineral component of bone. Calcium phosphate particles were precipitated in BC by consecutive incubation of calcium chloride and sodium phosphate solutions. Initial tests with osteoblasts in the in vitro evaluation showed that solid fusion between the material and the bone tissue is possible. Hence, this material is a good candidate for use as a therapeutic implant to regenerate bone and heal osseous damage. 

Orthopedic and dental implant materials bioceramics, 145-146 chemical modifications, 147-148 comparing mechanical properties of, and bone, 146 conventional, 127 costs, 126-127 current materials, 145-148 fate of implanted device, 140-141 integration into surrounding tissue, 127 integrin expression on osteoblasts, 144 integrins, 143-144 metals, ceramics, and polymers, 145 next generation, 127,148-159... 

CNTs are especially valued as implant materials thanks to their novel mechanical properties and surface functionability.35 They have been found to make an ideal scaffold for the growth of bone tissue.36 Moreover, many tissues and organs require bio-compatible substrates to facilitate tissue growth and implantation. The fabric made fom CNTs serves as an efficient tissue scaffold.36 Several publications demonstrate that CNTs can be used as a substrate for neuronal growth, and that modifications of the CNTs can be employed to modulate the development of neurons. This suggests that it may be possible to employ suitably functionalized CNTs as neural prostheses in neurite regeneration.35 Lipid bilayers have been developed using a nanotube template. 

Titanium is used in medicine mainly for its mechanical benefits in surgical and dental materials in a host of orthopedic and orthodontic appliances, with or without other metals (for example nickel, cobalt, chromium), and generally without serious adverse effects. Titanium and its alloys are in use as implants in bone surgery (1,2) and in dental materials (3,4). Research on the biocompatibility of metal and tissue continues (5). 

The end-stage healing response to biomaterials is generally fibrosis of fibrous encapsulation. However, there may be exceptions to this general statement (e.g., porous materials inoculated with parenchymal cells or porous materials implanted into bone). As previously stated, the tissue response to implants is in part dependent upon the extent of injury or defect created in the implantation procedure. 

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