Contact osteogenesis

Bioinert materials are materials that display minimal, if any, interaction with surrounding tissues examples of these are titanium and its alloys, alumina, partially stabilised zirconia, carbon and possibly ultrahigh molecular weight polyethylene (UHMWPE). In the case of bioinert materials bone remodelling occurs by a shape-mediated contact osteogenesis. 

As discussed in detail in Chapter 3.1, the advantage of bioinert materials is that they do not release any toxic constituents to the human body environment. However, on the downside they do not show positive interaction with living tissue. Instead, the body usually responds to these materials by forming a non-adherent fibrous capsule of connective tissue around the bioinert material that in the case of bone remodelling manifests itself by a shape-mediated contact osteogenesis. Consequently only compressive forces will be transmitted through the bone-biomaterial interfaces ( bony on-growth ). 

Figure 7.77 (a) Histological toluidine blue-stained sections of threaded Si-HAp implants after 7 days of implantation. Woven bone growth along and in direct contact with surfaces was observed (contact osteogenesis). This woven bone is mainly recognised by the numerous large osteocyte lacunae, (b) After... 

Muzzarelli et al. (2000) described a method for coating prosthetic articles with chitosan-oxychitin. Plates of titanium (Ti) and its alloys were plasma sprayed with hydroxyapatite and glass layers, and subsequently a chitosan coat was deposited on the plasma-sprayed layers using chitosan acetate. These layers were treated with 6-oxychitin to form a polyelectrolytic complex. This complex was optionally contacted with l-ethyl-3-(3-dimethylami-nopropyl) carbodiimide at 4°C for 2 hours to form amide links between the two polysaccharides, or acetylation with acetic anhydride in methanol to obtain a chitin film. In all cases, the modified coats were insoluble, uniformly flat, and smooth. Prosthetic materials coated with chitosan-oxychitin were capable of provoking colonization by cells, osteogenesis, and osteointegration. 

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