الفهرس 
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Abstract
This study was designed to investigate the effect of two marginal designs (chamfer –shoulder) on marginal adaptation and Fracture resistance of new full contour zirconia ceramic crowns.
A machined standard stainless steel dies representing maxillary first pre molar were constructed with different finish lines. A total number of twenty crowns were constructed (CAD\CAM milled) and classified into two equal groups, ten each, according to the type of the finish line used chamfer and shoulder.
All fabricated zirconia crowns were cemented on their respective dies using universal luting composite (Multilink) under static load.
Marginal adaptation was determined by measuring the space between the margin of the crown and the finish line of the preparation, using stereomicroscope at x32 magnification and image analysis software.
Fracture resistance was tested by universal testing machine, all observations were recorded and tabulated and subjected to statistical analysis.
Group A, crowns with chamfer design recorded higher marginal gap mean value (48.89 µm) while crowns with shoulder design recorded lower marginal gap mean value (26.32 µm) in group B.
Group B, crowns with shoulder design recorded higher fracture resistance mean value (3316 N) while crowns with chamfer design (group A) recorded lower fracture resistance mean value (3035 N).