Objectives: Shading of green-stage zirconia has previously been shown to affect to material strength. The aim of this study was to determine effect of experimental color shading agents on some mechanical properties of zirconia. Methods: 70 zirconia (ICE Zirkon, ZirkonZahn, Italy) discs (n=10/group) were divided into seven groups according to the different experimental color shading liquids the discs were dipped into: 1) Control discs were un-colored, 2) 2% ferrichloride (FeCl3), 3-4) 2% ferrichloride + 2% zirconiachloride (ZrCl4) + 2% yttriumnitrate [Y(NO3)] in two different proportions 10:1:1 and 10:2:2, 5) ZrCl4 containing 3Mol%Y, 6-7) 2% FeCl3 + 2% ZrCl4 (3Mol%Y) in two different proportions 10:1:1 and 10:2:2. All of the ceramic discs were sintered at 1500 °C in the sintering oven (ZirkonZahn). Biaxial flexural strength of the sintered discs (diameter 19mm, thickness 0.8mm) were measured dry at room temperature. Surface microhardness (VHN) was measured and the data was calculated using ANOVA-analysis. Results: Some of the shades revealed slightly lowered mechanical properties. Groups 2 and 5 had similar properties with the control group whereas groups 6 and 7 had some mechanical difference (p<0.05). No statistically significant difference (p>0.05) was found in terms of surface microhardness (VHN). Results were:
Group | Color shading agent | Flexural strength MPa (SD) | Vickers VHN (SD) |
1 | Control | 1132 (162)a | 1501 (194) |
2 | 2% FeCl3 | 1027 (96)ab | 1438 (117) |
3 | FeCl3:ZrCl4:Y(NO3) [10:1:1] | 998 (99)ab | 1469 (70) |
4 | FeCl3:ZrCl4:Y(NO3) [10:2:2] | 961 (101)ab | 1452 (57) |
5 | ZrCl4(3Mol%Y) | 1031 (102)ab | 1446 (44) |
6 | FeCl3:ZrCl4(3Mol%Y) [10:1] | 901 (120)b | 1488 (88) |
7 | FeCl3:ZrCl4(3Mol%Y) [10:2] | 958 (135)b | 1566 (84) |
*Different superscript letter describes statistical differences in flexural strength (p<0.05).
Conclusions: Some reduction in flexural strength of zirconia occurred in terms of using different experimental color shading agents.