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Zirconium oxide, known as zirconia, is a ceramic material with optimal esthetical and mechanical properties. Zirconia stabilized with yttrium oxide has the best properties for medical uses. A stress on ZrO z surface creates a crystalline modification that opposes to propagation of cracks. Zirconia core for fixed partial dentures (FPD) on anterior and posterior teeth and on implants are now available. Clinical evaluations after 3 years report good percentage of success for zirconia fixed partial denture. Zirconia biocompatibility was studied in vivo and in vitro by orthopedic research; no adverse responses were reported on insertion of ZrO z samples in bone or muscle. In vitro experimentation showed absence of mutation and a good viability of cells cultured on this material. Zirconium dioxide is white, has good wear resistance surface grinding could reduce toughness (6); also Kosmac and mechanical properties similar to a metal; it is also confirmed this assertion reporting a lower mean strength known as Zirconia. zr0 2 crystals and can be organized of zirconium oxide after surface grinding (7). Moreover, in different patterns: Monocline (M), Cubic (C) and ageing is another important feature of Zr0 2 ; Swan Tetragonal (T). In order to stabilize zirconium oxide it is reported that zirconia can lose its mechanical features if necessary to add other metallic oxides, such as MgO, CaO placed in a wet enviroment for a long time (8). and YP3; Yttrium stabilized zirconia nowadays is the

Zirconia, a biomaterial widely used in dentistry, has recently attracted much attention for its mechanical strength and toughness. Previously, its lack of mutagenic and carcinogenic power was reported. We describe here other essential aspects to be taken into account to define in vitro the biocompatibility of a material: the growth rate, viability, and adhesion capacity of normal stabilized cells growing on it. To this aim, immortalized RAT-1 fibroblasts, growing either on zirconia and on feldspatic (FE) ceramics were compared. In particular, the level of expression and the intra-and extra-cellular organization of fibronectin, a glycoprotein involved in cellular adhesion and migration during tissue repair, was analyzed. Fibroblasts cultured on zirconia showed a higher growth rate, and underwent necrosis at lower levels than cells on FE ceramic, whereas either materials did not stimulate apoptosis. Adhesion capacity of fibroblasts was evaluated measuring adherent cell nucleic acids with the fluorimetric CyQuant 1 assay, and it was found significantly higher in cells cultured on zirconia than on FE ceramic. This finding may be explained by the higher and more precocious expression of the adhesion protein fibronectin observed by indirect immunofluorescence in fibroblasts on zirconia. Overall, the results suggest that zirconia, exerting low cytotoxicity and strongly inducing adhesion capacity, increases cellular growth rate of fibroblasts. All these features suggest that zirconia could represent a more suitable biomaterial than FE ceramic for prosthesis in dentistry.2007 Wiley Periodicals, Inc. J Biomed Mater Res 86A: [959][960][961][962][963][964][965][966][967][968] 2008

Tantalum is obtained from the minerals colombite, tantalite and euxenite. It is greyish silver, heavy and very hard. Tantalum does not react with body fluids and is used to make surgical equipment. Tantalum also does not irritate the body and is used to make surgical sutures as well as implants, such as artificial joints and cranial plates. Bone growth around tantalum covered by calcium phosphate is described by in vitro experimentations. in vivo. Bioactive properties of porous tantalum have been recently developed. Porous tantalum consists of an interconnected porous structure with an average porosity diameter of approximately 400 microm. Hollow spheres with nanometre-to-micrometer dimensions are widely used in different range of applications such as drug delivery carriers and bioreactors. Porous tantalum metal is currently used in orthopaedic for manufacturing of structural component for primary and revision total hip and knee replacements and, more recently, in spine surgery. Good clinical outcomes have been achieved especially in hip revision surgery, using tantalum implants, and promising short term follow up have been reported for knee revision surgery. Some patents for tantalum biomedical applications have been obtained and this article reviews various recent patents on this material. Many patents are developed on tantalum for biomedical application. This paper review some of them with particular interested for biomedical applications in orthopaedic and dentistry.

Ceramic materials are made of an inorganic non-metallic oxide. Usually ceramics are divided into two groups: silicon ceramics and aluminous ceramics. Ceramics are also divided into crystalline and non-crystalline depending on inner molecular organization. Depending on their in vivo behaviour, ceramics are classified as bioresorbable, bioreactive or bioinert. Alumina and zirconia are bioinert ceramics; their low reactivity togheter with their good mechanical features (low wear and high stability) led to use them in many biomedical restorative devices. Their most popular application is in arthroprosthetic joints where they have proven to be very effective, that make their use suitable especially in younger, more active patients. Also dental use of these materials was proposed to achieve aesthetic and reliability of dental restorations. 2. Mechanical and chemical features of bioceramics 2.1 Alumina Corundum known as α-alumina is the alumina ceramic used for biomedical application,. In nature single crystals of this material are known as ruby if containing Cr2O3 impurities, or as sapphire if containing titanium impurities which give them blue colour. Al 2 O 3 molecule is one of the most stable oxides because of high energetic ionic and covalent bonds between Al and O atoms. These strong bonds (Alumina DG(298K) =1580 KJ/mol) leave the ceramic unaffected by galvanic reactions (absence of corrosion, e.g. absence of ion release from bulk materials and from wear debris). Adverse conditions such as strong acidic or alkaline environment at high temperatures didn't corrupt allumina properties. Under compression allumina showed good resistance but under tensile strength shows its brittleness. at room temperature alumina does not show plastic deformation before fracture (e.g. no yield point in stress-strain curve before fracture), and once started fractures progress very rapidly (low toughness K IC). Tensile strength of alumina improves with higher density and smaller grain size. A careful selection of raw materials and a strict control of production process are performed by manufacturers to optimize allumina mechanical properties. Introduction of low melting MgO in the ceramic process enhanced mass transport during solid state sintering so that www.intechopen.com