الفهرس 
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Abstract
The aim of this in-vitro study was to evaluate the color stability, fatigue resistance, and marginal integrity of three different CAD / CAM resin-based ceramic materials (Vita Enamic, Brilliant Crios, and Shofu Hc). The CAD/CAM blocks of each material were sectioned using a low-speed diamond saw under copious water irrigation. A total number of eighteen rectangular specimens were cut 12x14x2, six specimens in each group. Baseline shade was measured, then the specimens were immersed in coffee for 12 days taken out of their vials, rinsed with distilled water and wiped with air spray and gauze. Color was then remeasured using Vita easy shade to evaluate the color stability. Fifteen crowns, five for each group were milled using MXCL milling machine. Each crown was seated on a 3D printed die and vertical marginal gap before cementation was measured using a USB digital microscope. Crowns were cemented using Panavia F2.0 adhesive resin cement under 3 kg load then the marginal gap was remeasured. Before fatigue testing, thermocycling of the crowns was done for 5000 cycles, and then each crown was subjected to fatigue testing using a chewing simulator by applying cyclic loading of 50 N for 250,000 cycles with a loading frequency of 1.6 Hz. The vertical marginal gap of the survived crowns was measured. The survived crowns were subjected to static load to fracture using the universal testing machine with a metallic rod with a round tip 3.8 mm in diameter using a crosshead speed of 1 mm/min. Results showed a non-statistically significant difference in mean ΔE in the three groups. Shofu Hc showed a higher ΔE than brilliant crios and Enamic. All the crowns survived the fatigue testing. There was a statistically significant difference in mean Max. load between Shofu Hc and brilliant crios. Shofu Hc showed a higher Max. Load than Enamic and Crios. Marginal gap results showed a statistically significant difference between all groups and through all stages ( before or after cementation and after thermomechanical aging).