Interface Residual Stresses in Dental Zirconia Using Laue Micro-diffraction

Due to their aesthetic value and high compressive strength, dentists have recently employed ceramics for restoration materials. Among the ceramic materials, zirconia provides high toughness and crack resistant characteristics. Residual stresses develop in processing due to factors including grain anisotropy and thermal coefficient mismatch. In the present study, polychromatic X-ray (Laue) micro-diffraction provided grain orientation and residual stresses on a clinically relevant zirconia model ceramic disk. A 0.5 mm x 0.024 mm region on zirconia was examined on a 500 nm scale for residual stresses using a focused poly-chromatic synchrotron Xray beam. Large stresses ranging from – to + 1GPa were observed at some grains. On average, the method suggests a relatively small compressive stress at the surface between 47 and 75 MPa depending on direction. Introduction Typical core restorative materials in modern dentistry include alumina, zirconia, or noble metal alloys that are veneered with porcelain. Zirconia provides high toughness and crack resistant characteristics. The phase transformation from tetragonal to monoclinic produces local volume expansion favoring crack closure and results in additional strength. However, during crown fabrication in dental laboratories, residual stresses develop due to factors including grain anisotropy, thermal coefficient mismatch, and the overall complex tooth geometry. Along with stress induced phase changes, grain-grain stresses are significant. In the present study, polychromatic X-ray (Laue) 1 micro-diffraction provided grain orientation and residual stresses on clinically relevant disk shaped dental zirconia. The ceramic disk was fabricated considering dental laboratory thermal history and material properties typically utilized for dental restorations. The deviatoric strains developed within zirconia, as a result of grain anisotropy and the coefficient thermal expansion mismatch, were determined by highly focused polychromatic 368 Copyright ©JCPDS-International Centre for Diffraction Data 2009 ISSN 1097-0002