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KMID : 0362220130400040271
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Journal of The Korean Research Society for Dental Materials
2013 Volume.40 No. 4 p.271 ~ p.280
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The effect of thermo and mechanical cycling on the fracture resistance of ceramic core-porcelain veneer
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Kim Jeong-Mi
Bae Ji-Myung
Oh Seung-Han
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Abstract
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The incidence of repeated forces during chewing results in stress concentration, and thermal variations induce fatigue of the materials themselves and/ or the interface between them. This study was to evaluate the effect of thermo and mechanical cycling on the fracture resistance between ceramic core and veneering ceramic. Four kinds of ceramic system (ICE Zircon, IPS e.max, Z match, and Lava Zirconia) were used to prepare ceramic core-porcelain veneer system and NiCrMo bonding alloy (Dentarium, Germany) was used to make metal ceramic system (MCS) as a control. We fabricated metal master die with upper diameter of 7.95 mm, bottom diameter of 9.00 mm, height of 5.00 mm, and taper of 6°. The thickness of metal coping was 0.3 mm, while those of the ceramic copings of all ceramic crowns were 0.5 mm. By adding dentin and enamel ceramics on each coping, crowns with total occlusal thickness of 1.5 mm were fabricated. The specimens were submitted to 20,000 thermal cycles between 5℃ and 55℃ with a dwelling time of 30 seconds. Mechanical cycling loaded 16,000 cycles under 20N lode. Fracture resistances were measured by a universal testing machine (Z020, Zwick, Germany) with a crosshead speed of 1 mm/min. The fracture resistance was analyzed using a one-way ANOVA followed by Tukey HSD test at α=0.05. The results of racture resistance of MCS and Lava Zirconia were significantly greater than the other groups (p<0.05). The failure modes of e.max were cohesive failures within ceramic coping and those of ICE Zircon, Z match, and Lava Zirconia were adhesive failures between ceramic coping and veneering ceramic. MCS showed mainly adhesive failures between metal coping and veneering ceramic.
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KEYWORD
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zirconia, fracture resistance, all ceramic crown, metal ceramic crown
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