The aim will be to analyze the interfacial energy for fracture (fracture toughness) of the bond between resin cement and zirconia. The comparison will be made between infiltrations made by the sol-gel method with quick immersion in silicic acid, in TEOS or the glass infiltration of a graded zirconia (slurry). Therefore, brazil nut specimens will be infiltrated by the following methods: Silica sol-gel infiltration (~ 40 minutes) with silica obtained by silicic acid or TEOS and glass infiltration by slurry as proposed by Zhang & Kim (2009). After infiltration, the surfaces will be etched with hydrofluoric acid and a silane containing MDP will be applied. The resin cement will be applied on the surfaces, and two hemi-discs will be cemetend under 750g load to standardize the thickness. 24 hours after cementation, the Brazil nuts will be tested in a universal testing machine (Instron). The test will be performed using angles (crack inclination toward the application of load) of 1 °, 5 °, 10 ° and 15 °. The critical load for fracture of the interface will be used for calculating the energy release rate G. When a compressive load is applied to the Brazil nut, the crack is subjected to a combination of tensile mode I and shear mode II .The specimen is under pure tensile at 0 ° and pure shear at 25 °. At the end of testing all samples will be observed under SEM to characterize the failures. The characterization of how the fracture evolved inside and among the materials will be made with Energy Dispersive Spectroscopy (EDS). Only failures that occur at the interface between zirconia and cement will be considered.
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