Comparison of Fracture Strength between two Systems: IPS Empress 2 and IPS E.max press

Statement of problem: One of the major problems of all-ceramic restorations is their probable fracture against lateral forces. However there is not enough information about fracture strength of various all-ceramic restorations.Propose: The aim of this experimental research was to compare the fracture strength and the most probable fracture points in all-ceramic restorations. In this laboratory-based experimental study, 10 symmetric crowns from each IPS Empress2 and IPS e.max press system were constructed on a laboratory model for maxillary central incisor with 2mm occlusal reduction and deep chamfer finishing line. The core thickness was between 0.7-0.8 mm and porcelain was placed over the core using the layering technique. Each of the crowns was cemented onto the dye using Dual cure Variolink II cement and were imposed to compressive forces in Universal testing machine (V=1mm/min) at 30 degrees angle in palatal surface until the fracture occurred. Then the samples were inspected for fracture points by observation. The statistical evaluations were done with Independent Sample T-test (α=0.05). The average force leading to fracture was 385 N (SD=79/96) for IPS Empress2 and 380 N (SD=106/28) for IPS e.max press. The most common fracture points in two groups were the incisal edge and buccal surface. There was no meaningful statistical difference in fracture force between the two systems (P>0.05).The findings of this research indicated that there is no meaningful statistical difference between these two systems in their fracture strength.therefor they are both suitable for constructing anterior all-ceramic restorations.