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This study is to evaluate the effect of thermocycling on the shear-bond strength between ceramic core and veneering ceramic. Three kinds of ceramic system (ICE Zircon, IPS e.max, and Lava Zirconia) were used to prepare ceramic core-porcelain veneer system and NiCrMo bonding alloy(Dentarium, Germany) were used to make metal ceramic system(MCS) as a control. 10 specimens per each experimental group were fabricated according to the Schmitz-schulmeyer system. Prepared samples were put into the thermocycling system(KD-TCS30, Kwangduk P.A, Korea). The samples were circulated between 5℃ and 55℃ bath with the interval of 30 seconds. The times of circulation in this research are 20,000 and 50,000, respectively. The results of shear-bond strength showed that there was a significant difference between thermocycled groups and non-thermocycled groups(P＜0.05). In group of non-thermocycled groups, the values of MCS and ICE Zircon were significantly higher than those of IPS e max and Lava Zirconia. However) on the condition of thermocycled groups) Lava only showed significant reduction of bond stregnth with proportional to the circulation time(P＜0.05) and other groups did not show any significant difference between conditions(P＞0.05). In terms of failure mode of specimens, all experimental groups showed combined failure mode including adhesive and cohesive failure. Therefore, among three zirconia core materials, ICE Zircon indicated excellent shear-bond strength after 50000 thermocycling process and is expected to be one of more suitable combinatory system compared to MCS system.
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