Influence of Different Cementation Materials and Thermocycling on the Fracture Resistance of IPS e.max Press Posterior Crowns

Abstract

Aim: To evaluate the effect of different cementation materials and thermocycling on the fracture resistance of IPS e.max Press posterior crowns. Materials and methods: Thirty-two sound maxillary molars were subjected to a standardized preparation in order to receive IPS e.max Press (Ivoclar Vivadent) ceramic crowns. Another 16 molars were left unprepared to serve as control (Group I). Both Panavia F2.0 (Kuraray) and Relay X Unicem (3M ESPE) luting cements were used to fix the fabricated crowns (n=16 for each) to their respective prepared teeth (Groups II and III respectively). Eight specimens from each of the 3 test groups were randomly selected for further thermocycling (5000 cycles). All specimens were then vertically pressed using anatomical metal attachment affixed to the upper member of a universal testing machine and running at crosshead speed of 1mm/min. The collected data were statistically analyzed using 2-way analysis of variance (ANOVA) and Student's t-test at 5% level of significance. Results: The load values that the restored teeth can withstand (From 907 to 986 N) was much lower than that recorded for normal teeth (1279 N) (2-way ANOVA test, p 0.05). Thermocycled specimens showed lower values of fracture loads in comparison to non-thermocycled ones (Student t test, p<0.001). Conclusions: Either kinds of cement materials used looks to have no effect on the fracture resistance of IPS e.max crowns to vertical loads. Thermocycling adversely affects the ability of the cemented crowns to resist the applied load. The fracture loads of the tested crowns exceeded the recorded values of normal occlusal forces.