en ترمیمی Cosmetic and Restorative Dentistry پژوهشي Research Objectives <p> To compare the viscoelastic behavior (creep) of dental resin-composites under both static and cyclic loading in compression.</p>Methods <p> Ten cylindrical specimens (4<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >×<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >6<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm), divided into two subgroups (<i>n</i><img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >=<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >5) were prepared from each of four commercial resin-composites, using a divisible stainless steel mold. They were thoroughly cured from all sides. Groups 1 and 2 were loaded statically and dynamically respectively after 1<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >d of fabrication and dry storage. Group 1 was loaded with a constant static load of 35<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >MPa and it was applied for 2<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >h followed by 2<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >h of strain recovery to obtain the static creep (%) and permanent set (%) respectively. To Group 2 a cyclic load between 1<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >MPa and 50<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >MPa was applied at a frequency of 0.25<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >Hz for 30<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >min to obtain the “dynamic” creep strain (%). Regression and correlation analysis (<i>α</i><img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >=<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >0.05) was performed to examine possible correlations between static and “dynamic” creep.</p>Results <p> For the resin-composite investigated, a good correlation was found between “dynamic” creep strain (%) and maximum static creep strain (%) (<i>r</i><img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >=<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >0.92) and a strong correlation was also found between “dynamic” creep strain (%) and permanent set (%) (<i>r</i><img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >=<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >0.97), Significance: Maximum static creep was significantly higher than “dynamic” creep. A direct numerical equivalence was not expected between static and “dynamic” creep values, as in the case of “dynamic” creep, loading was cyclic and was applied for a shorter overall period. Nevertheless a strong correlation was found between the static and dynamic creep measurement.</p><hr><p></p><p> <strong> Source: </strong>Dental Materials </p><p><a href="http://www.demajournal.com/article/S0109-5641(11)00928-6/abstract" target="_blank"><font color="#0000cc">  Full text </font></a></p> Resin composite, Static creep, Dynamic creep, Viscoelastic stability, Cyclic loading, Mechanical properties 0 0 http://idai.ir/browse.php?a_code=A-10-32-262&slc_lang=en&sid=1 • Muhammad Kaleem 10031947532846001056 10031947532846001056 Yes • Konstantinos • Masouras 10031947532846001057 10031947532846001057 No • Julian • D. Satterthwaite 10031947532846001058 10031947532846001058 No • Nick Silikas 10031947532846001059 10031947532846001059 No • David • C. Watts 10031947532846001060 10031947532846001060 No