Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

This in vitro study assessed the fracture resistance of endodontically treated molar teeth restored with resin nano ceramic (lava ultimate) endocrowns compared to lithium disilicate (IPS e.max CAD) endocrowns. Eight extracted mandibular second molar teeth were endodontically treated. The preparations were done with 2 mm intracoronal extensions of the endocrowns into the pulp chamber. Teeth divided into 2 groups (n = 4); each group was restored with standardized CAD / CAM fabricated endocrowns using one of the two tested materials (group 1: IPS e. max CAD {EX}, Ivoclar vivadent, schaan, liechtenstein, group 2: Lava ultimate {LU}, 3M ESPE, germany). After cementation with resin cement (RelyX ultimate resin cement), specimens were subjected to fatigue loading (250,000 cycles corresponding to 1 year of clinical service). A compressive load (N) was applied to the long axis of the teeth using a universal testing machine until failure and fracture. The failure load was recorded, and specimens were examined visually under a magnifying lens and photographically professional camera for modes of failure: favorable type above CEJ; and unfavorable type below CEJ. The t. test was used to compare the fracture load of two groups, and type of fracture p = 0.05

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