Evaluation of the internal fit and marginal gap of highly translucent Prettau zirconia crowns with two different degree of occlusal convergence / Mostafa Mahmoud Mohamed Hussein ; Supervised Omnia Elshihy , Ashraf Taher Kheir Eldean

Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prothodontics

The aim of this study was to evaluate the effect of convergence angle (12{u00B0}-20{u00B0}) of tooth preparation on the internal fit and marginal accuracy of monolithic zirconia crowns. Electron microscope was used to measure marginal gap and internal fit, two metal dies constructed with two different total convergence angles 12{u00B0}and 20{u00B0}. Fourteen total samples was divided into two groups, seven constructed zirconia crowns via CAD/CAM system for 12{u00B0}and seven for 20{u00B0}. The crowns were held by a jig to measure the marginal using gap by digital microscope. Data were presented as means and standard deviation (SD) value. Student{u2019}s t-test was used for comparison between two taper degrees. Pearson{u0341}{u0341}{u0341}s correlation coefficients was used to determine significant correlation between marginal, axial and occlusal gap distances.Statistical analysis was performed with SPSS® (statistical package for scientific studies) statistics version 22 for windows. It was found that 12{u00B0} preparation taper show statistical significance higher mean marginal gap distance, it was found that no statistical significant difference between mean axial gap distance of both 12{u00B0} and 20{u00B0} taper andit was found that no significant difference between mean occlusal gap distance with the two taper degrees. Marginal adaptation of die with convergence angle 20{u00B0}is better than die with convergence angle 12{u00B0}. Internal fit not changed by occlusal convergence

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