The effects of viscoelastic parameters on residual stress development in a zirconia/glass bilayer dental ceramic

Taskonak, Burak; Borges, Gilberto A.; Mecholsky, John J.; Anusavice, Kenneth J.; Moore, B. Keith; Yan, Jiahau

doi:10.1016/j.dental.2008.01.004

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Volume 24, Issue 9 , Pages 1149-1155, September 2008

The effects of viscoelastic parameters on residual stress development in a zirconia/glass bilayer dental ceramic

Burak Taskonak
- Department of Restorative Dentistry, Indiana University School of Dentistry, Indianapolis, Indiana, USA
- Corresponding author at: Department of Restorative Dentistry, Division of Dental Biomaterials, Indiana University School of Dentistry, 1121 West Michigan Street, Indianapolis, IN 46202, United States. Tel.: +1 317 274 3725; fax: +1 317 278 7462/7808.
Gilberto A. Borges
- Assistant Professor, Department of Dental Materials and Restorative Dentistry, University of Uberaba, Uberaba, Brazil
John J. Mecholsky Jr.
- Department of Materials Science and Engineering, College of Engineering, University of Florida, Gainesville, Florida, USA
Kenneth J. Anusavice
- Department of Dental Biomaterials, College of Dentistry, University of Florida, Gainesville, Florida, USA
B. Keith Moore
- Department of Restorative Dentistry, Indiana University School of Dentistry, Indianapolis, Indiana, USA
Jiahau Yan
- Department of Restorative Dentistry, Indiana University School of Dentistry, Indianapolis, Indiana, USA

Received 31 July 2007; received in revised form 8 January 2008; accepted 12 January 2008.

Abstract

Objectives

The aim of this study was to test the hypothesis that the residual stresses in a zirconia-based bilayer dental composite system can be tailored through heat treatment above and below the glass transition temperature of glass veneers.

Methods

Ceramic bilayer disc specimens were prepared from a zirconia core and a glass veneer. Each bilayer ceramic group was heat treated 40°C below, 20°C and 40°C above and at the glass transition temperature of the glass veneer, and cooled using a fast or a slow cooling rate. Specimens were tested for flexure strength using a biaxial bending fixture. Residual stresses were calculated using a fracture mechanics approach.

Results

Heat treatments produced significant differences (p≤0.05) between the mean flexural strengths of the heat treatment groups when the specimens were cooled using a fast cooling rate. However, there was not a significant difference (p>0.05) between the mean flexural strengths of the heat treatment groups when a slow cooling rate was used. Fractures initiated from the veneer surfaces of the specimens.

Significance

Heat treatment above and below the glass transition temperature of the veneer layer, and the cooling rate have a significant effect on the flexural strength of the bilayer ceramic laminates. The existence of residual compressive stress is the most likely reason for the observed strength increases. Residual stresses can be modified using the elastic-viscoelastic relaxation behavior of a glass veneer.

Keywords: Bilayer ceramic, Residual stress, Fracture mechanics, Viscoelasticity