FRACTURE STRENGTH OF THE IPS EMPRESS CROWN:THE EFFECT OF OCCLUSAL DEPTH AND AXIAL INCLINATION ON UPPER FIRST PREMOLAR CROWNS

Dong, Jin Keun; Oh, Sang Chun; Kim, Sang Don

Abstract

The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the occlusal depth (1.5mm, 2.0mm, 2.5mm) and axial inclination (4degree, 8degree, 12degree) of the upper first premolar. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and each crown was cemented on each metal die with resin cement. The cemented crowns mounted on the testing jig were inclined 30 degrees and a universal testing machine was used to measure the fracture strength. The results were : 1. The fracture strength of the ceramic crown with 2.5mm depth and 12degreeinclination was the highest (630N). Crowns of 1.5mm depth and 4degreeinclination had the lowest strength(378N). There were no significant differences of the fracture strength by axial inclination in same occlusal depth group. 2. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the margin, irrespective of occlusal depth.