The aim of this study is to evaluate how chemical and hydrothermal progressive aging affect the optical properties of two monolithic zirconia (anterior and posterior). Methods: Twenty disks of each zirconia will be obtained from pre-sintered zirconia blocks, the discs will be painted and sintered(final dimensions: 12 mm in diameter and 1.2 mm in height). Will be 4 experimental groups (n = 10): Group 1: Anterior monolithic zirconia; Group 2: Posterior monolithic zirconia; after sintering the 20 disks of each zirconia will be randomly divided into 2 sub-groups according to the aging performed (A: hydrothermal B: chemical). Initial characterization will be made by SEM to illustrate and posterior microstructure comparison; X-ray diffraction to identify and quantify crystalline phases present and optical properties analysis in a portable spectrophotometer. After initial characterization specimens will be submitted to aging and progressive characterization: hydrothermal, in an autoclave at 120 ° C and 1.2 kgf / cm2 of pressure at the times: 5h, 8h, 12h and 15h; chemical, in acetic acid at 4%, at the times: 90h, 120h, 180h and 150h. Between each aging time the specimens will be subjected to the same initial analyzes. Statistical analysis will be done with normality and comparison tests among the materials, subgroups and proposed times.
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