Partially-sintered Kavo zirconia blocks (Kavo Corp., Germany) with the same batch and the same after-sintered size of 11×10×5 mm were used in this study. The specimens were cut and milled by Kavo CAD/ CAM system (Kavo Corp., Germany). Afterwards, the specimens were ground by 120, 200, 400, 600, 800, and 1000 grit SiC paper sequentially, and polished adopting 15 μm diamond paste. They were sandblasted by alumina particles of 120 µm at 0.15 MPa for 20 seconds. Finally, the specimens were cleaned by ultrasonic cleaning for 10 min, and dried by infrared drying light. The veneering process was performed using KISS veneering porcelain (Degudent Corp., Germany) on the fully sintered zirconia, and the sintering process was performed by Ney Centurion Q 50 porcelain furnace (Ney Dental Inc, American).