Hydrothermal degradation methods affect the properties and phase transformation depth of translucent zirconia

Author(s)

de Araujo-Junior, Everardo N. S. ^[1] ; Bergamo, Edmara T. P. ^[1] ; Campos, Tiago M. B. ^[2] ; Jalkh, Ernesto B. Benalcazar ^[1] ; Lopes, Adolfo C. O. ^[1] ; Monteiro, Kelli N. ^[3] ; Cesar, Paulo F. ^[3] ; Tognolo, Fernanda C. ^[1] ; Tanaka, Ricardo ^[4] ; Bonfante, Estevam A. ^[1]

Affiliation

^[1] Univ Sao Paulo, Bauru Sch Dent, Dept Prosthodont & Periodontol, 9-75 Otavio Pinheiro Brisola, BR-17012901 Bauru, SP - Brazil

^[2] Technol Inst Aeronaut, Dept Phys, Sao Jose Dos Campos, SP - Brazil

^[3] Univ Sao Paulo, Dept Biomat & Oral Biol, Sch Dent, Sao Paulo, SP - Brazil

^[4] TNK Lab, Rua Joao de Santa Maria, 129 Jardim Saude, Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS; v. 112, DEC 2020.
• Web of Science Citations: 0

Abstract

Objectives: To characterize the optical and mechanical properties of a commercial and in-house translucent Y-TZP before and after aging in autoclave or hydrothermal reactor. Methods: In-house experimental discs were obtained through uniaxial and isostatic pressing a translucent Y-TZP powder and sintering at 1,550 degrees C/1 h. Commercial discs were milled from pre-sintered blocks fabricated with the same powder through uniaxial and isostatic pressing and sintering. Discs were allocated into three groups ac-cording to aging condition: immediate, aged via autoclave, or reactor (134 degrees C, 20 h, 2.2 bar). Crystalline content and microstructure were evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Residual compressive stress (CS) was determined by Raman spectroscopy. Optical properties were determined by the contrast ratio (CR) and translucency parameter (TP) using reflectance data. Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength tests. Results: XRD and SEM revealed a typical Y-TZP crystalline content, chiefly tetragonal phase, and a dense crystalline matrix for both processing protocols. Reactor aging triggered a more pronounced t-m transformation relative to autoclave. In-house and commercial Y-TZPs demonstrated similar CR and TP, with reactor aging significantly increasing their translucency. Similarly, reactor aging influenced Vickers hardness and fracture toughness. In-house processed Y-TZP clearly demonstrated the presence of CS, whereas commercial Y-TZP showed no presence of CS. Non-aged in-house Y-TZP resulted in significantly lower characteristic strength relative to commercial Y-TZP. While aging protocols significantly increased the characteristic strength of inhouse Y-TZP, reactor significantly decreased commercial Y-TZP characteristic strength. Both Y-TZP processing protocols demonstrated high reliability at high-stress missions, with no detrimental effect of aging. Conclusions: Laboratory aging methodology significantly influenced optical and mechanical properties of a commercial and in-house translucent Y-TZP. (AU)

• FAPESP's process: 19/08693-1 - Experimental glass-infiltrated alumina-zirconia composites: characterization of microstructure, optical and mechanical properties.
• Grantee: Edmara Tatiely Pedroso Bergamo
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 19/14798-0 - Development of pre-sintered ZTA 80% Al2O3/20% ZrO2 composite blocks for milling in CAD/CAM system
• Grantee: Adolfo Coelho de Oliveira Lopes
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 12/19078-7 - Development and processing of Al2O3-ZrO2 translucent composite for CAD/CAM monolithic prostheses: the effect of aging on biaxial flexural strength
• Grantee: Estevam Augusto Bonfante
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 19/00452-5 - EXPERIMENTAL 70%Al2O3-30%ZrO2 ZTA COMPOSITES: MECHANICAL, ESTRUCTURAL AND TOPHOGRAPHICAL CHARACTERIZATION
• Grantee: Ernesto Byron Benalcazar Jalkh
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 16/18818-8 - Multi-User Equipment approved in grant 2012/19078-7: ElectroPuls E3000 Linear-Torsion All-Electric dynamic test instrument package
• Grantee: Estevam Augusto Bonfante
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 18/03072-6 - Experimental 70% Al2O3-30% ZrO2 composites: structural characterization and survival probability before and after aging
• Grantee: Ernesto Byron Benalcazar Jalkh
• Support Opportunities: Scholarships in Brazil - Doctorate