en ترمیمی Cosmetic and Restorative Dentistry پژوهشي Research Objectives <p> The C-Factor has been used widely to rationalize the changes in shrinkage stress occurring at the tooth/resin-composite interfaces. Experimentally, such stresses have been measured in a uniaxial direction between opposed parallel walls. The situation of adjoining cavity walls has been neglected. The aim was to investigate the hypothesis that: within stylized model rectangular cavities of constant volume and wall thickness, the interfacial shrinkage-stress at the adjoining cavity walls increases steadily as the C-Factor increases.</p>Methods <p> Eight 3D-FEM restored Class I ‘rectangular cavity’ models were created by <i>MSC.PATRAN/MSC</i>.<i>Marc</i>, <i>r2-2005</i> and subjected to 1% of shrinkage, while maintaining constant both the volume (20<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm³) and the wall thickness (2<img alt="AWT IMAGE" src="webfiles/images/transparent.gif" width="4" height="1" >mm), but varying the C-Factor (1.9–13.5). An adhesive contact between the composite and the teeth was incorporated. Polymerization shrinkage was simulated by analogy with thermal contraction. Principal stresses and strains were calculated. Peak values of maximum principal (<strong>MP</strong>) and maximum shear (<strong>MS</strong>) stresses from the different walls were displayed graphically as a function of C-Factor. The stress-peak association with C-Factor was evaluated by the Pearson correlation between the stress peak and the C-Factor.</p>Results <p> The hypothesis was rejected: there was no clear increase of stress-peaks with C-Factor. The stress-peaks particularly expressed as <strong>MP</strong> and <strong>MS</strong> varied only slightly with increasing C-Factor. Lower stress-peaks were present at the pulpal floor in comparison to the stress at the axial walls. In general, <strong>MP</strong> and <strong>MS</strong> were similar when the axial wall dimensions were similar. The Pearson coefficient only expressed associations for the maximum principal stress at the <i>ZX</i> wall and the <i>Z</i> axis.</p>Significance <p> Increase of the C-Factor did not lead to increase of the calculated stress-peaks in model rectangular Class I cavity walls.</p><hr><p></p><p> <strong> Source: </strong>Dental Materials </p><p><a href="http://www.demajournal.com/article/S0109-5641(11)00864-5/abstract" target="_blank"><font color="#0000cc">  Full text</font></a></p> Finite element analysis, Shrinkage stress, Resin-composites, Class I, Bonded restorations, C-Factor 0 0 http://idai.ir/browse.php?a_code=A-10-32-248&slc_lang=en&sid=1 Flávia P. Rodrigues 1003194753284600989 1003194753284600989 Yes Nick Silikas 1003194753284600990 1003194753284600990 No David C. Watts 1003194753284600991 1003194753284600991 No Rafael Y. Ballester 1003194753284600992 1003194753284600992 No