Impact of different pretreatments and aging procedures on the flexural strength and phase structure of zirconia ceramics. Issue 10 (October 2019)

• Record Type: Journal Article
• Authors: Kelch, Matthias; Schulz, Julian; Edelhoff, Daniel; Sener, Beatrice; Stawarczyk, Bogna
• Is Part Of: Dental materials. Volume 35:Issue 10(2019)
• Page Start: 1439
• Page End: 1449
• Publication Date: 2019-10
• Subjects: Zirconia ceramics -- Flexural strength -- Air-abrasion -- Aging -- Monoclinic phase; Dentistry -- Periodicals; Dental materials -- Periodicals; 617.695
• DOI: 10.1016/j.dental.2019.07.020
• Languages: English
• ISSNs: 0109-5641

Abstract

Graphical abstract: Highlights: Pretreatment through air-abrasion affects the flexural strength of 3Y-TZP0.25 . Aging influences the flexural strength of 3Y-TZP0.25 . Least impact after air-abrasion with 30 μm silica-coated alumina powder. Increasing monoclinic phase content (FM ) with increasing particle size and pressure. 50 and 105 μm alumina-coating leads to higher FM -values after 5 years of dry storage. Abstract: Objective: To test the impact of zirconia pretreatment and aging on flexural strength and phase structure. Methods: For flexural strength measurements, 180 3Y-TZP0.25 specimens were fabricated and pretreated: (i) air-abraded (105-μm alumina, 0.25 MPa), (ii) air-abraded (50-μm alumina, 0.25 MPa), (iii) air-abraded (30-μm silica-coated alumina, 0.28 MPa) (iv) non-pretreated. Each pretreated group (n = 15) was aged: (a) hydrothermal (134 °C, 0.23 MPa, 2 h) (b) in a mastication simulator (1, 200, 000×, 5/55 °C) and (c) not aged. The fractured specimens were stored dry for 5 years (23 °C) for analysis of phase transformation. Additionally, specimens were fabricated from 3Y-TZP0.25 (n = 12) and 3Y-TZP0.05 (n = 8), pretreated (i, ii, iii, iv), and hydrothermally aged. Each air-abrasion method was alternated using 0.05, 0.25 and 0.4 MPa pressure. The phase transformation was examined by Raman spectroscopy and surface topography by scanning electron microscope. Data were analyzed using univariate ANOVA with the Scheffé post hoc test and partial-eta-squared (ƞp ²) (α = 0.05). Results: The highest impact on flexural strength was exerted by the pretreatment (ηP ² = 0.261, p < 0.001), followed by interactions between pretreatment and aging (ηP ² = 0.077, p = 0.033). Non-pretreated and non-aged specimens showed the lowest monoclinic percentage. Hydrothermal aging and 5 years of storage at room temperature increased the monolithic percentage of 3Y-TZP0.25 . The highest phase transformation was observed in groups air-abraded with 105-μm alumina particles. Increasing pressure during the air-abrading process increased the content of the monoclinic phase in zirconia surfaces. Significance: Air-abrasion with 30-μm silica-coated alumina powder can be recommended for pretreatment of 3Y-TZP0.25 and 3Y-TZP0.05 . For air-abrasion using alumina powder lower pressure should be used.