ISPUB.COM The Internet Journal of Dental Science Volume 6 Number 2 1 of 7 Influence of Different Cementation Materials and Thermocycling on the Fracture Resistance of IPS e.max Press Posterior Crowns M Abou-Madina, K Abdelaziz Citation M Abou-Madina, K Abdelaziz. Influence of Different Cementation Materials and Thermocycling on the Fracture Resistance of IPS e.max Press Posterior Crowns. The Internet Journal of Dental Science. 2008 Volume 6 Number 2. 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<0.001). No significant difference in the fracture load values was detected among the groups of restored teeth (986 MPa and 974 N for groups II and III) (Student t 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. INTRODUCTION In spite of the amazing success of metal-ceramic crowns 1 , 2 their known drawbacks, such as questionable marginal esthetic and biocompatibility, were directed the attention toward the use of metal-free restorations. 34 In the last 2 decades several manufacturers had introduced new ceramic systems having the ability to overcome the hereditary brittleness and low fracture toughness of early ceramic materials. 5 These features together with excellent esthetic, biocompatibility, resistance to wear and low thermal conductivity nominated many of the current all-ceramic systems to pass the challenge expected to face when applied in the posterior region of the mouth. 6 , 7 , 8 , 9 , 10 Heat-pressing is a process that has been developed to overcome the inhomogeneities and porosity that occur during creaming. 11 , 12 The first heat-press ceramic material (IPS Empress, Ivoclar –Vivadent, Schaan, Liechtenstein) is a type of leucite-reinforced glass ceramic and has a flexural strength of 182 MPa. 12 A modified version of this material (IPS Empress 2) having lithium disilicate (2 Sio 2 - Li 2 O) crystals could provide an average fracture strength of 350 MPa. Therefore, it was nominated not only for anterior 3 unite bridges, but also for restoration of posterior region which may include a first premolar as a pontic. 13 An improved press ceramic material called IPS e.max Press (Ivoclar –Vivadent) was recently introduced specially for posterior and bridge applications. The new material consists of lithium disilicate pressed glass ceramic like that of IPS