الفهرس 
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Abstract
This study was designed to investigate the effect degree of taper on marginal adaptation and fracture resistance of CAD/CAM zirconia core.Three machined milled standard stainless steel dies were prepared to stimulate lower first molar preparation to receive all ceramic crown with three different degree of taper (6°, 12°, 22°). The master stainless steel dies were duplicated using silicon mold after which fifteen crowns were produced using epoxy resin material having the same modulus of elasticity of dentin.Epoxy resin dies were divided into three groups, five specimens each according to the degree of taper. Each group received CAD/CAM zirconia coping. Marginal adoption of all specimens was determined y measuring space between the margin of the core and the finish line of preparation, using cone beam computed tomography. All specimens were loaded until fracture using universal testing machine to indicate the fracture resistance of each group then statistical analysis was carried out. The results showed significant difference between three tested groups in marginal adaption, where 22 degree had significantly better fit also there was significant difference between three tested groups in fracture resistance, where 22 degree have showed higher fracture load.