Fracture strength of the IPS empress crown : the effects of incisal reduction and axial inclination on upper canine / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the incisal reduction (2.0mm, 2.5mm, 3.0mm) and axial inclination (4degrees., 8.degrees, 12degrees.) of the upper canine. MATERIALS AND METHODS: 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 the universal testing machine was used to measure the fracture strength. RESULTS: 1. The fracture strength of the ceramic crown with 3.0mm depth and 12degrees inclination was the highest (839N). Crowns of 2.0mm depth and 12degrees inclination had the lowest strength (559N). 2. There was no significant difference in the fracture strength by axial inclination in the same incisal reduction group. 3. 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 incisal reduction.

A study on the stress distribution of the all ceramic crowns according to the cusp angle of the maxillary first premolar using three dimensional finite element method / 대한치과보철학회지

STATEMENT OF PROBLEM: Clinically, maxillary first premolar has a high risk of fracture. This is thought to be caused by the susceptible figure which the maxillary first premolar has. In other words, sharp cusp angles of the premolar is thought to influence this situation. PURPOSE: This study was to know stress distribution of all-ceramic crown according to the cusp angle. MATERIAL AND METHOD: It was manufactured a three dimensional finite element model simplified maxillary first premolar, and then analyzed stress distribution when cusp angle was each 80 degrees, 90 degrees, 100 degrees, 110 degrees and 120 degrees. RESULTS AND CONCLUSION: 1. The von Misses stress showed that stress decreases as cusp angle increases in the central groove of the occlusal surface. 2. It showed that maximum principal stress was centered at the region of the central groove of the occlusal surface and a region which the force was inflicted. And also it appeared high on the lingual and buccal side of finish line. 3. The X axis of normal stress was focused in the central groove of the occlusal surface. The Y axis normal stress appeared high in the central groove of the occlusal surface, buccal and lingual side. 4. The Stress near the finish line showed a low value compared with stress in the region of the central groove of the occlusal surface. 5. It shows that the most dangerous angle for tooth fracture was on 80 degrees of the cusp angle and low on 120 degrees of its.