Mechanical properties and translucency of a multi-layered zirconia with color gradient for dental applications

In this work, the properties of yttria-stabilized zirconia-based ceramics, Y-TZP containing Fe2O3 as coloring agent were evaluated. Nanoparticled powder of 3Y-TZP (ZrO2 - 3 mol.% Y2O3) doped with different amounts of Fe2O3 (0.002-0.136 wt%) were compacted into monolithical or multilayered samples and sintered at 1475 degrees C - 2 h. The samples were characterized by X-ray diffraction analysis (XRD), relative density, scanning electron microscope (SEM). Hardness and fracture toughness in the color interface were investigated using the Vickers indentation method and the biaxial flexural strength was determined by the piston on 3 balls method (P-3B). Furthermore, optical parameters were measured using spectrophotometry in regard to sample thickness and Fe2O3 content. The results indicated a good adhesion between layers, proven by indentation cracks randomly growing between different regions, because the powders used produced very similar morphological characteristics. The different amounts of Fe2O3 studied in this work did not interfere in densification, phase composition, or microstructure of the sintered ceramics. The fracture toughness and flexural strength did not significantly change due to the addition of Fe2O3, presenting values close to 7 MPa m1/2 and 1120-1150 MPa, respectively, in all studied compositions. On the other hand, increasing Fe2O3 contents lead to an increase in the hardness of the material (1280-1330 H V), and higher contrast ratios (CR) with a consequent loss of translucency. Color variation (Delta E) depended also on the thickness of the material.

Automated summary

The properties of yttria-stabilized zirconia-based ceramics containing Fe2O3 as a coloring agent were evaluated in this work. The addition of Fe2O3 did not interfere with densification, phase composition, or microstructure of the sintered ceramics, but increased the material hardness and contrast ratios, leading to a loss of translucency.