Effect of Fe2O3 Addition and Sintering Temperature on mechanical Properties and Translucence of Zirconia Dental Ceramics with Different Y2O3 Content

Manuel Fellipe R P Alves,Claudinei Dos Santos,Kurt Strecker,Sebastião Ribeiro,Paulo A Suzuki

doi:10.1590/1980-5373-mr-2020-0402

Abstract

The influence of Fe2O3 additions on the microstructure, mechanical properties and translucence of zirconia with 3 mol-% or 5 mol-% Y2O3 was evaluated. Samples were pressed with different thickness and sintered at 1475, 1500, 1550 and 1600°C for 2 h. Density, phases, microstructure, roughness, strength and translucency were analyzed. All samples showed densification greater than 99%. After sintering at 1600°C, the phase analysis revealed only tetragonal ZrO2 in samples with 3% Y2O3, while in samples with 5% Y2O3 the cubic ZrO2 phase was identified. Significant increase in the grain size was noted, when increasing the Y2O3 content from 3% to 5% from 0.8 µm to 2.3 µm for sintered samples at 1600°C. The strength was affected with Y2O3 content and no relevant influence of the Fe2O3 on density, microstructure or mechanical properties. Visible reflectance spectroscopy analyses, related to the CIELab scale, indicate variation in the contrast ratio as function of thickness of samples and coloring agent Fe2O3 content.

Highlights

Over the past few decades, the demand for dental prostheses an aesthetic appearance of natural teeth has stimulated an intense technological rush to replace the metallic infrastructure in prostheses[1]
As we have demonstrated in our recent publication[36], working with the same compositional range of Fe2O3, the coloring additive did not have a significant impact in the microstructure of the ZrO2 based ceramics
The increase of the yttria content of the ZrO2 powders from 3 mol% to 5 mol% resulted in significant changes of the phase composition and microstructure of the sintered materials

Summary

Introduction

Over the past few decades, the demand for dental prostheses an aesthetic appearance of natural teeth has stimulated an intense technological rush to replace the metallic infrastructure in prostheses[1] In this scenario, structural ceramics emerged as potential substitutes and so-called “metal free” prosthesis systems have been developed entirely composed of ceramic materials[2]. ZrO2 stabilized with 3 mol% Y2O3, technically known as 3Y-TZP, exhibits outstanding mechanical properties due to the stabilization of the tetragonal phase This phase, t-ZrO2, is metastable at room temperature and may undergo transformation into the stable, monoclinic phase, in the wake of a tensile stress field of a crack. This transformation is accompanied by a volume change in the order of 4% to 5%, creating itself compressive stresses in the matrix, which hinders crack propagation and resulting in the highest fracture toughness of all ceramic materials[4,5,6]

Methods

Results

Conclusion