الفهرس 
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Abstract
1. This study was conducted to compare the fracture resistance of different designs of IPS Empress II all ceramic restorations made on endodontically treated teeth.
2. Thirty human mandibular molars were selected to be approximately having the same dimensions; teeth were endodontically treated then devided into three groups of 10 teeth each.
3. Teeth in group I were prepared for onlay restoration, group II were prepared for restoration with conventional crown while group III were prepared for modified endocrown restoration. Restorations then were made from IPS Empress II and placed and cemented on their corresponding teeth.
4. All specimens were then subjected to thermal and mechanical loading.
5. Cemented restorations were mounted on the universal testing machine with a steel spherical tip with a diameter of 6 mm installed in.
6. Vertical force was derived gradually onto the center of the occlusal surface at a speed of 1mm/min till fracture. The forces of fracture were observed and recorded in Newton.
7. All the results were statistically analyzed using Oneway ANOVA and Tukey HSD tests.