On the mechanical properties and microstructure of zirconia-reinforced feldspar-based porcelain

The aim of this study was to produce and to evaluate the mechanical properties of a dental feldspar-based porcelain reinforced by zirconia particles. The specimens were prepared by incorporating different volume fractions (10, 20, 30, 40 or 50%) of zirconia particles (3Y-TZP) in a porcelain matrix. The mixtures were hot pressed in vacuum at 970 °C for 2 min. Flexural strength of the composites was measured using a three-point-bending test. Hardness, Young's modulus and fracture toughness were also measured for all the composites. The microstructure and fracture surfaces were characterized by Field Emission Guns Scanning Electron Microscopy (FEG-SEM). Chemical analyses were performed by Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). The highest flexural strength (218±24 MPa) and fracture toughness (2.1 ± 0.1 MPa m^1/2) values were recorded for composites containing 30% zirconia particles. That corresponded to improvement in mechanical properties of about 2 times relative to those recorded for feldspar-based porcelain. It was not noticed any significant difference in hardness values. The Young's moduli also increased with the addition of zirconia particles. The addition of zirconia particles to porcelain improved significantly the mechanical properties of the resultant material. Zirconia-reinforced porcelain can constitute a promising alternative to conventional feldspar-based porcelains to produce prosthetic restorations, mainly for posterior teeth where high strength and toughness are demanded.