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The purpose of this study was to compare the fracture strength of five kinds of all-ceramic crowns (Vintage, Dicor, Empress-staining, Empress-layering, In-Ceram) luted with glass ionomer cement and composite resin cement and to evaluate the effect of cements on the fracture strength of all ceramic crowns. Five groups of twelve uniform sized all-ceramic crown specimens were fabricated. Six specimens of each group were cemented with glass ionomer cement (Fuji G.I. cement) and the remaining six specimens of each group were etched, silane-treated, and cemented with composite resin cement(Bistite resin cement). The crowns were stored in water (37℃) for 1 day prior to loading in an Instron, using a steel ball(diameter 4mm) at a crosshead speed of 0.5mm/min. The crowns were angled 30˚, so the steel ball contacted with the crowns 2mm lingual from the mid-incisal edge. @ES The results obtained were summarized as follows: @EN 1. With G.I. cement, mean fracture load (Kg) were: intage : 18.33±1.47 ; Empress-staining : 23.92±6.67 ; Dicor : 24.0±5.81 ; Empress-layering : 26.92±2.80 ; In-Ceram : 51.58±6.87 ; ANOVA revealed a significant difference existed (p<0.05) between the group A (Vintage, Dicor, Empress-staining, Empress-layering) and group B (In-Ceram). 2. With Resin cement, mean fracture load (Kg) were: Intage : 22.75±4.97 ; Dicor : 42.75±7.07 ; Empress-staining : 44.08±7.99 ; Empress-layering : 50.42±5.43 ; In-Ceram : 52.58±6.51 ; ANOVA revealed a significant difference existed (p<0.05) between the group A(Vintage) and B (Dicor, Empress-staining, Empress-layering, In-Ceram). 3. Resin cement ignificantly increased the fracture strength of the all-ceramic crowns for Dicor (156%), Empress-staining (185%), Empress-layering (187%) (p<0.05) ; but did not increase the fracture strength of Vintage (128%) and In-Ceram (101%) (p>0.05). 4. Majority of the all-ceramic crowns show a wedge fracture extending through proximal surfaces to an apex, usually apical third (with G.I. cement) or middle third (with Resin cement) of the facial surface.
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