The mechanical performance of dental ceramic materials is commonly approached experimental by measuring the fracture strength, which reflects its static behavior. In normal service dental restorations are loaded far below their critical load, either continuously or under repetitive conditions. Unlike static stress, which is analyzed with calculations for a single stress state, fatigue damage occurs when stress at a point changes over time. The objective of the present study is to compare alternative loading areas of molar zirconia crowns with different designs, veneered with various overpressing ceramics and to predict the biomechanical behavior of the prosthetic restored teeth after cyclic loading, using a FEA. The fatigue behavior of various all-ceramic restorations will be investigated using a wide range of load levels (400-3200 N) till 108 cycles, during axial and para-axial loading. The Fatigue Safety Factor was calculated, and values less than one indicated failure before the design life is reached. The failure behavior was interpreted relative to the load levels, areas, and restoration designs. Axial loading led to fatigue failure at lower loads (500 N) compared to para-axial loading (2000 N). Related to the crown design, the failure behavior didn't change significant.
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