Ultra-translucent zirconia processing and aging effect on microstructural, optical, and mechanical properties

Everardo N S de Araújo-Júnior; Edmara T P Bergamo; Tiago M C Bastos; Ernesto B Benalcázar Jalkh; Adolfo C O Lopes; Kelli N Monteiro; Paulo F Cesar; Fernanda C Tognolo; Rafael Migliati; Ricardo Tanaka; Estevam A Bonfante

doi:10.1016/j.dental.2022.02.016

Ultra-translucent zirconia processing and aging effect on microstructural, optical, and mechanical properties

Dent Mater. 2022 Apr;38(4):587-600. doi: 10.1016/j.dental.2022.02.016. Epub 2022 Mar 7.

Affiliations

¹ Department of Prosthodontics and Periodontology, University of São Paulo, Bauru School of Dentistry, Bauru, SP, Brazil. Electronic address: everardonapoleaojr@gmail.com.
² Department of Prosthodontics and Periodontology, University of São Paulo, Bauru School of Dentistry, Bauru, SP, Brazil.
³ Department of Physics, Technological Institute of Aeronautics, São José dos Campos, SP, Brazil.
⁴ Department of Biomaterial and Oral Biology, University of São Paulo, School of Dentistry, São Paulo, SP, Brazil.

PMID: 35272865
DOI: 10.1016/j.dental.2022.02.016

Abstract

Objectives: To evaluate the effect of the ceramic processing and aging method on the microstructure, optical, and mechanical properties of a third generation ultra-translucent zirconia, yttria partially stabilized zirconia (5Y-PSZ).

Methods: In-house discs were obtained through uniaxial and isostatic pressing an ultra-translucent Y-PSZ powder and sintering at 1450 °C for 2 h. As control, a commercial disc was milled from pre-sintered blocks fabricated with the same 5Y-PSZ powder through isostatic pressing and sintered under the same protocol. Discs were allocated into three groups according to aging condition as immediate (non-aged) and aged using autoclave or hydrothermal reactor at 134ºC for 20 h at 2.2 bar. Crystalline content and microstructure were evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Optical properties were determined using reflectance data to calculate the contrast ratio (CR) and translucency parameter (TP). Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength tests.

Results: XRD spectra revealed a prevalence of cubic (70%) and tetragonal (30%) phases, and the SEM images showed a dense fully crystalline ceramic matrix for both materials. Crystalline content and microstructure of the in-house and commercial 5Y-PSZs were not affected by aging. As-sintered 5Y-PSZs demonstrated similar CR (~0.6) and TP (~18) values, as well as Vickers hardness (~14 GPa) and fracture toughness (~3.8 Mpa.m^1/2), with no significant alteration after both aging methods. In-house and commercial Y-PSZs Weibull moduli ranged from 3.0 to 5.3. 5Y-PSZ processing methods resulted in similar characteristic strength after sintering (592-618 Mpa). While commercial 5Y-PSZ showed no significant influence of aging on strength, hydrothermal reactor aging significantly decreased the in-house Y-PSZ characteristic strength (474 Mpa). Both 5Y-PSZs demonstrated high reliability up to 300-Mpa strength missions, with no detrimental effect of aging (88-100%).

Significance: Irrespective of the processing method, ultra-translucent 5Y-PSZ showed high aging resistance and translucency stability, as well as strength corresponding to the indication up to short-span anterior prostheses.

Publication types

Research Support, Non-U.S. Gov't
Review

MeSH terms

Ceramics
Dental Materials*
Materials Testing
Powders
Reproducibility of Results
Surface Properties
Yttrium
Zirconium*

Substances

Dental Materials
Powders
Yttrium
Zirconium
zirconium oxide