en ترمیمی Cosmetic and Restorative Dentistry پژوهشي Research Objectives <p> The veneering process of frameworks induces residual stresses and can initiate cracks when combined with functional stresses. The stress distribution within the veneering ceramic as a function of depth is a key factor influencing failure by chipping. This is a well-known problem with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objective of this study is to investigate the influence of veneer thickness on the stress profile in zirconia- and metal-based structures.</p>Methods <p> The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. The stress profile was measured in bilayered disc samples of 20<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm diameter, with a 1<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm thick zirconia or metal framework. Different veneering ceramic thicknesses were performed: 1<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm, 1.5<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm, 2<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm, 2.5<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm and 3<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm.</p>Results <p> All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth up to 0.5–1.0<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm from the surface, and then becoming compressive again near the framework, except for the 1.5<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm-veneered zirconia samples which exhibited interior tensile stresses. Stresses in the surface of metal samples were not influenced by veneer thickness. Variation of interior stresses at 1.2<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm from the surface in function of veneer thickness was inverted for metal and zirconia samples.</p>Significance <p> Veneer thickness influences in an opposite way the residual stress profile in metal- and in zirconia-based structures. A three-step approach and the hypothesis of the crystalline transformation are discussed to explain the less favorable residual stress development in zirconia samples.</p><hr><p></p><p> <strong> Source: </strong>Dental Materials </p><p><a href="http://www.demajournal.com/article/S0109-5641(11)00901-8/abstract" target="_blank"><font color="#0000cc">  Full text </font></a></p> Residual stress, Hole-drilling, Zirconia, Veneering ceramic, Thickness 0 0 http://idai.ir/browse.php?a_code=A-10-32-252&slc_lang=en&sid=1 Amélie K. Mainjot 10031947532846001004 10031947532846001004 Yes Gary S. Schajer 10031947532846001005 10031947532846001005 No Alain J. Vanheusden 10031947532846001006 10031947532846001006 No Michaël J. Sadoun 10031947532846001007 10031947532846001007 No