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Optical and mechanical characterization of a translucent and ultratranslucent zirconia: effect of ceramic processing and aging method

Araújo Junior, Everardo Napoleão Santana De

Biblioteca Digital de Teses e Dissertações da USP; Universidade de São Paulo; Faculdade de Odontologia de Bauru 2021-09-01

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  • Título:
    Optical and mechanical characterization of a translucent and ultratranslucent zirconia: effect of ceramic processing and aging method
  • Autor: Araújo Junior, Everardo Napoleão Santana De
  • Orientador: Bonfante, Estevam Augusto
  • Assuntos: Zirconia; Ceramicas; Envelhecimento; Propriedades Ópticas; Propriedades Mecânicas; Zirconia; Optical Properties; Mechanical Properties; Ceramics; Aging
  • Notas: Tese (Doutorado)
  • Descrição: Objectives. To characterize the optical and mechanical properties of a commercial and experimental translucent 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and ultra-translucent 5 mol% yttria-partially stabilized zirconia (Y-PSZ) before and after aging in autoclave or hydrothermal reactor. Materials and Methods. In-house experimental discs were obtained through uniaxial and isostatic powders pressing and sintering at 1,550°C/1h for 3Y-TZP and 1450/2h for 5Y-PSZ. 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 according to aging condition: immediate, aged in autoclave or hydrothermal reactor (134ºC, 20h, 2.2bar). Crystalline content and microstructure were evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). 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 (50 %), and a dense crystalline matrix for both processing protocols. Hydrothermal reactor aging triggered a more pronounced monoclinic transformation (44%) relative to autoclave (27%) in the 3Y-TZP samples. XRD spectra revealed a prevalence of cubic (70%) and tetragonal (30%) phases, and the SEM images showed a dense fully crystalline ceramic matrix for 5Y-PSZs. In-house and commercial 3Y-TZPs demonstrated similar CR and TP, with reactor aging significantly increasing their translucency. Similarly, hydrothermal reactor aging influenced Vickers hardness and fracture toughness. As-sintered 5Y-PSZs demonstrated similar CR and TP values, as well as Vickers hardness and fracture toughness, with no significant alteration after both aging methods. Non-aged experimental 5Y-TZP resulted in significantly lower characteristic strength relative to commercial 3Y-TZP. While aging protocols significantly increased the characteristic strength of the in-house 3Y-TZP, hydrothermal reactor significantly decreased commercial 3Y-TZP characteristic strength. 5Y-PSZ processing methods resulted in similar characteristic strength after sintering. While commercial 5Y-PSZ showed no significant influence of aging on strength, hydrothermal reactor aging significantly decreased the in-house 5Y-PSZ characteristic strength. Conclusion. Laboratory aging methodology significantly influenced optical and mechanical properties of a commercial and experimental translucent 3Y-TZPs. Ultra-translucent 5Y-PSZ showed high aging resistance and translucency stability.
  • DOI: 10.11606/T.25.2021.tde-09122021-083744
  • Editor: Biblioteca Digital de Teses e Dissertações da USP; Universidade de São Paulo; Faculdade de Odontologia de Bauru
  • Data de criação/publicação: 2021-09-01
  • Formato: Adobe PDF
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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