Production and characterization of yttria stabilized zirconia ceramic blocks for dental applications

Kaplan, Melis
Dense zirconia ceramic blocks were produced by pressureless sintering at temperatures down to 1350- 1450 oC for dental applications. The effect(s) of integration of cold isostatic pressing (CIP’ing) to the production procedure of the zirconia blocks was researched by applying 80, 100, and 150 MPa isostatic pressure. The effect of color infiltration solutions (NiCl2 and MoCl3 solutions) on color and low temperature degradation properties of zirconia was investigated. Tetragonal to monoclinic phase transformation was identified by X-ray diffraction (XRD) analysis. The microstructure and grain size of the samples were examined by scanning electron microscope (SEM). Density was measured by Archimedes method. Compressive strength, Vickers hardness, and fracture toughness were evaluated with respect to sintering temperature. Color assessments were made by measuring CIE Lab L*, a*, b* and ΔE* values. Hydrothermal degradation sensitivity of the samples were evaluated by performing LTD test. Result of the XRD and SEM analyses as well as density, hardness, and fracture toughness measurements revealed that 100 MPa CIP pressure and 1450 oC sintering temperature were the optimum parameters for the production of 3 mol % yttria stabilized zirconia ceramic blocks. A block produced at 100 MPa CIP pressure and subsequently sintered at 1450 oC revealed 99.86 % theoretical density. Coloring solutions containing 0.1 and 0.25 wt % MoCl3 provided clinically acceptable color for dental applications with the ΔE* value ranging from 5.16 to 6.42. Aging sensitivity LTD tests revealed that both colored and uncolored samples are compatible with the standards.