Purpose: The aim of this in vivo study was to evaluate the clinical outcome of all-ceramic crowns fabricated by dental CAD/CAM GN-I (GC, Japan).Methods: A total of 125 patients were treated in 306 teeth (153 anterior teeth, 105 premolars, and 53 molars). This evaluation describes the results after a mean follow- up time of 23 months with a range from 12 to 34 months after cementation. Results: Five crowns (1 anterior tooth, 3 premolars, and 1 molar) fractured, and in all of the 5 cases the insufficient thickness of ceramic crowns was the reason for failure. Conclusion: All clinical performances of all-ceramic crowns except 5 cases were excellent. Thickness of ceramic crowns was important to prevent fracture after cementation