ABSTRACT
Statement of Problem: One of the major problems of the all ceramic restorations is their probable fracture against the occlusal force. However, there is not enough information about fracture resistance of all the ceramic crowns in different finishing lines
Purpose: The aim of present in-vitro study was to compare the effect of two marginal designs [shoulder and chamfer] on the fracture resistance of all ceramic restorations, Inceram
Methods and Material: On an extracted caries-free first maxillary premolar a 50-degree chamfer margin [0.7 mm] was prepared. Ten impressions were taken using a polyvinylsiloxane. The impressions were poured with epoxy resin to fabricate the dies. The same tooth was retrieved and the 50-degree chamfer was converted into a 90-degree shoulder margin [1mm]. Ten impressions were prepared and 10 more epoxy resin dies were fabricated. The impressions of each epoxy resin die were taken using polyvinylsiloxane impression material and poured with die stone. Alumina cores with a thicknes of 0.5mm were fabricated on the stone dies in a dental laboratory. The alumina cores were then cemented with panavia on the epoxy resin dies and underwent a fracture test with a universal testing machine. The samples were then investigated regarding the origin of the failure. The statistical analysis was done using T-test
Result: The mean value of the fracture resistance for the chamfer samples was 610.18+/-58.79 N and that of the shoulder samples was 502.72+/-105.83 N. The student's T-test revealed a statistically significant difference between the groups [p <0.05]
Conclusion: The results of this study indicate a relationship between the marginal design and fracture resistance. A chamfer margin could improve the biomechanical performance of the posterior single crown alumina restorations. This might be due to the strong unity in the chamfer margin