Eight commercial pre-sintered zirconia ceramics (Table 1: GC ST, GC HT and GC UHT, GC, Tokyo, Japan;
Katana HT, Katana ML, Katana STML and Katana UTML, Kuraray Noritake, Tokyo, Japan; Lava Plus, 3M
Oral Care, Seefeld, Germany) were cut into dimensions of approximate by 15 × 15 × 3.5 mm, 18 × 18 × 3.5 mm or 12 × 12 × 3.5 mm, depending on the thickness of the pre-sintered ceramic blank provided by the suppliers. All specimens were cut through whole ceramic pre-sintered disk in order to include all the layers in the analysis. Specimens were pressureless sintered in air according to the manufacturers' instructions (Table 1) using a computer-programmed furnace (Nabertherm, Lilienthal, Germany) reaching the final specimen dimensions of (1) ≈10 × 10 × 1.2 mm for GC ST and GC HT; (2) ≈12 x 12 x 1.2 mm for Katana HT, Katana ML, Katana STML, Katana UTML and Lava HT; (3) ≈15 × 15 ×
1.2 mm for GC UHT. The sintered materials were ground plane parallel and gradually polished down to 1 µm with diamond suspensions and finally with colloidal silica until a mirror-glass surface was achieved. The final specimen thickness was 0.5 ± 0.05 mm for evaluating the microstructure and optical properties and 1.2 ± 0.05 mm for analyzing the biaxial flexural strength.
Katana HT, Katana ML, Katana STML and Katana UTML, Kuraray Noritake, Tokyo, Japan; Lava Plus, 3M
Oral Care, Seefeld, Germany) were cut into dimensions of approximate by 15 × 15 × 3.5 mm, 18 × 18 × 3.5 mm or 12 × 12 × 3.5 mm, depending on the thickness of the pre-sintered ceramic blank provided by the suppliers. All specimens were cut through whole ceramic pre-sintered disk in order to include all the layers in the analysis. Specimens were pressureless sintered in air according to the manufacturers' instructions (Table 1) using a computer-programmed furnace (Nabertherm, Lilienthal, Germany) reaching the final specimen dimensions of (1) ≈10 × 10 × 1.2 mm for GC ST and GC HT; (2) ≈12 x 12 x 1.2 mm for Katana HT, Katana ML, Katana STML, Katana UTML and Lava HT; (3) ≈15 × 15 ×
1.2 mm for GC UHT. The sintered materials were ground plane parallel and gradually polished down to 1 µm with diamond suspensions and finally with colloidal silica until a mirror-glass surface was achieved. The final specimen thickness was 0.5 ± 0.05 mm for evaluating the microstructure and optical properties and 1.2 ± 0.05 mm for analyzing the biaxial flexural strength.