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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

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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