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The purpose of this study was to compare the fracture strength of the IPS-Empress ceramic crown according to margin types such as bevel, shoulder, ronuded shoulder, schouler with bevel, rounded shoulder with bevel and bevel with groove. After 10 metal dies were constructed for each group, the IPS-Empress ceramic crown were fabricated and each crown was cemented on each metal die with Bistite resin cement. The cemented each crown was cemented on each metal die with Bistirte resin cement. The cemented crowns mounted in the resting jig were inclined 30 degree and universal testing machine (Zwick 1456 41, Zwick Co., Germany) was used to measure the fracture strength. The obtained result were as follows : 1. The fracture strenght of the crown with reounded shoulder was the hightest of all. The mean fracture strength was 484N in rounded shoulder, 357N in bebel, 341N in rounded shoulder with bevel, 300N in shoulder with bevel, 280N in shoulder and 275N in bevel with groove. 2. The fracture strength of rounded shoulder was statistcally different from those of shoulder with bevel, shoulder and bevel with groove. 3. In the strain at fracture, there was no significant difference among each group. 4. The fracture mode of the crown was simila and most of fracture line began at the loading area and extended throught proximal surface perpendicularly to the margin, irrespective of margin type.
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