Y-TZP zirconia has been the most promising material in dental restorations as it presents biocompatibility combined by high mechanical properties, especially in the first and second generation. Despite the advances in Y-TZP research since its introduction in the commercial market, some limitations still persist, such as the need to improve the translucency properties to imitate the appearance of the natural tooth. This problem was solved with the third generation, however with drastic reduction in mechanical properties. One strategy to overcome this obstacle was the development of the fourth generation of zirconia, which consists of multilayer blocks in which each layer contains a different composition and crystalline structure of tetragonal and cubic phase. Although this new material presents promising prospects, it has just arrived on the market. Therefore, little is known about its behavior in humid conditions of the oral environment, as well as resistance to the application of cyclic loads throughout its useful life. Understanding the nucleation and mechanisms of crack propagation is essential to prevent the occurrence of failures. In addition, understanding the variations that affect the translucency property are important in maintaining a proper prosthetic aesthetics. Therefore, it is necessary to carry out in vitro studies of accelerated aging in order to predict the clinical behavior of the material in the long term. To solve these doubts, the objective of this work is to make an exhaustive study of the interface between the layers to verify what are the effects caused on the mechanical, optical (translucency) and mechanical (longevity in fatigue) properties. As it presents difficulties in sectioning these multilayer blocks, this work proposes the elaboration of bilayer samples, which respect the manufacturing configuration of the original blocks using the 3Y-TZP and 5Y-TZP type zirconia as a base. The study will be developed around commercially available materials and will carry out tests of biaxial flexion, nano-hardness, micro-hardness, failure analysis, microstructural investigation, study of the diffusion profile, hydrothermal treatment and fatigue test.
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