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배태성,원대희,이민호,최운재,문영윤 한국생체재료학회 2004 생체재료학회지 Vol.8 No.3
This study was performed to evaluate the fracture toughness of two pressable glass-ceramic materials : Empress 2 and an experimental glass-ceramic material. Ten discs per material were prepared. Fracture toughness was measured by indentation fracture method. Vickers-produced indentation crack was made using a Vickers hardness tester at a load of 49.0 N and dwell time of 15 sec. Radial crack propagation at interface glass-ceramic core region was examined. Fracture toughness of the Empress 2 and experimental glass-ceramic material, EGC, were 1.20 and 1.30 MPa톗1/2, respectively. The finest lath-shaped interlocking microstructures of lithium disilicate crystals were observed in the Empress 2 and EGC, but the crystal shape of EGC was shotter than Empress 2. Lateral chipping was rapidly propagated toward veneer porcelain at the interface between glass-ceramic core and veneer porcelain. The EGC showed no sign of delamination between the glass-ceramic core and veneer porcelain but the Empress 2 showed a sign of delamination.