Effects of coloring agents applied during sintering on bending strength and hardness of zirconia ceramics.

The effects of coloring agents (Vita in-ceram 2000 YZ coloring liquid (VL) and IPS e.max ZirCAD (IS)) and shades (1, 3, and 5) applied during sintering on the bending strength and fracture toughness of zirconia ceramics was examined. No differences in the bending strength or fracture toughness were observed for the type of coloring agent used. Moreover, the bending strength and Vickers hardness of the zirconia ceramics decreased, while the crack length and fracture toughness did not change with the different coloring agents. The marginal borders of the indentations formed were clear and linear, and no damage, including chipping, was observed. Therefore, clinical application of zirconia ceramics can be recommended because the coloring agents and shades applied during sintering have the same effect as an opaque layer and cause no significant deterioration of the mechanical properties of the zirconia ceramics.