Effect of In Vitro Ageing on a Cold Isostatic-Pressed Zirconia Ceramic for All Ceramic Restorations

Abstract:

High strength of Yttria stabilized tetragonal zirconia polycrystal (Y-TZP) zirconia ceramics are sensitive to low temperature degradation (LTD) that leads to exaggerated tetragonal to monoclinic transformation and a surface to depth propagating degradation that diminishes their mechanical properties. In vitro tests for accelerating ageing have been proposed for the prediction of zirconia ceramics clinical performance. The aim of the present work was to investigate the in vitro ageing of a cold isostatic-pressed zirconia ceramic for all ceramic restorations. Bar-shaped specimens milled from a zirconia block (Ivoclar IPS e.max ZirCAD) were sintered to full density, mirror-polished and cut into two equal pieces. One piece was used as control while the other was subsequently aged (steam 134°C / 2 bars / 10 hours). Atomic Force Microscopy (AFM) was used to evaluate the surface profile and the micro-structural features before and after ageing. Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction Analysis (XRD) were used to determine the degree of the m-ZrO₂ transformation. Ageing resulted in an increase of the surface roughness, while the formation of monoclinic spots on the surface of the specimens was verified by surface uplifts in the AFM images. The peaks of the m-phase were clearly observed in the FTIR spectra while an average increase of 16% w.t. of the m-ZrO₂ phase was recorded by XRD. Although, no sound lifetime predictions can be made from accelerated tests, based on the ISO standard that imposes that the m-phase should not exceed 25% wt after 5h at 134 °C and 2 bar pressure , it can be concluded that the tested ceramic resisted an extreme transformation that could negatively affect its clinical performance.

• Periodical: Key Engineering Materials (Volumes 493-494)
• Pages: 604-608
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.493-494.604
• Online since: October 2011
• Authors: A. Vatali, E. Siarampi, Eleana Kontonasaki, Nikolaos Kantiranis, T. Zorba, N. Vouroutzis, Konstantinos M. Paraskevopoulos, Petros Koidis
• Keywords: AFM, Aging, Cold Isostatic-Pressed Zirconia Ceramic, FT-IR, X-Ray Diffraction (XRD)

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