الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
Abstract
This study was designed to evaluate the effect of different margin designs and two cement types on the fracture resistance of full-contour monolithic lithium disilicate and translucent zirconia crowns.
Three stainless steel crowns were designed to simulate all ceramic full coverage crown preparation for a premolar tooth. Three different margin designs were prepared: knife edge, chamfer and radial shoulder. An occlusal bevel was prepared for exact positioning of the copings during measurements.
Impressions of the master dies were made with a silicone duplicating material using plastic tubes. The impressions of the master dies were poured using a non-shrink epoxy resin material for the measurement of fracture resistance.
Twenty full contour crowns were designed on the scanned epoxy dies for each margin design, using inLab 3D software (V3.8), and then were milled using translucent zirconia blocks and lithium disilicate blocks, ten for each material.
The translucent zirconia crowns were milled with an oversize of approximately 25% to compensate for the later sintering shrinkage. The crowns were sintered in high temperature furnace to have maximum density. While the lithium disilicate crowns were adjusted in the pre-crystallized state and then were glazed and crystallized.The crowns were then seated and cemented. In each group half of the specimens were cemented with glass ionomer and the other half were cemented with resin cement. During cementation static finger pressure was applied then the specimens were axially loaded with a 5kg load using a specially designed device.
After cementation, the specimens were screwed to an attachment which was screwed to the base of the machine. The specimens were then loaded vertically on their occlusal surfaces. The loading piston was centered along the long axis of the specimens. The specimens were then loaded in the universal testing machine under a thrust speed of 0.5mm/min.
Three-Way ANOVA test was used to examine the effect of the different margin designs and cement types on the fracture resistance of monolithic lithium disilicate crowns and translucent zirconia crowns.
The results revealed that the fracture resistance of translucent zirconia crowns was significantly higher than that for lithium disilicate crowns regardless the type of margin design and the cement type. While the radial shoulder and chamfer margin designs showed significantly higher fracture resistance than knife edge. Resin cement showed higher fracture resistance than glass ionomer cement.