الفهرس 
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Abstract
Objectives: The purpose of this in vitro study was to evaluate and compare the fracture resistance of CAD/CAM zirconia reinforced lithium silicate glass ceramic (Vita suprinity) endo-crown and conventional glass fiber post supported crowns in molars and premolars maxillary teeth. Materials and Methods: A total 60, devitalized human, 30 maxillary premolars(group A) and 30 maxillary molars (group B) restored by vita suprinity. Each group was subdivided to 3 subgroups (10 each) according to the design of the preparation; group A1: (n= 10) endodontically treated upper premolars with 2mm ferrule and deep chamfer finish line restored with glass fiber posts, composite core and restored with reinforced crowns. group A2: (n= 10) endodontically treated upper premolars with butt joint margin restored with reinforced endocrown. group A3: (n= 10) endodontically treated upper premolars with 2mm ferrule and deep chamfer finish line restored with endocrown. group B1: (n= 10) endodontically treated upper molars with 2mm ferrule and deep chamfer finish line restored with glass fiber posts, composite core and restored with reinforced crowns. group B2: (n= 10) endodontically treated upper molars with butt joint margin restored with reinforced endocrown. group B3: (n= 10) endodontically treated upper molars with 2mm ferrule and deep chamfer finish line restored with reinforced endocrown. All crowns were cemented with dual cure Rely X U200 self-adhesive resin cement. The specimens were thermocycled (3500 cycle, between 5oC-55oC). Then mounted in the Universal Testing Machine. Mode of failure was also examined. Data were analyzed using one way analysis of variance (ANOVA) and Tukey’s post hoc significance difference tests. Differences were considered significant at P<0.05. Results: There was statistically significant difference between Groups B1 and B3 and also between Groups B1 and B2 (p<0.001) among studied molar teeth. Groups B3 and B2 were not significantly different from each other (p=0.3). The higher mean fracture resistance was detected among Groups B1 then B3 and least for B2 (1056.90 ± 168.54, 624.83 ± 126.04 & 557.30±156.80N), respectively. In premolars teeth groups. Statistically significant difference between Groups A1 and A3 and also between Groups A1 and A2 (p<0.001). Groups A3 and A2 were not significantly different from each other (p=0.57). The higher mean fracture resistance maximum load was detected among Groups A1 then A3 and least for A2 (1069.23±126.97, 544.70±105.33 & 512.33±146.36N) respectively. Conclusions: Under the conditions of this study, fracture resistance load obtained in different test groups restored by Vita suprinity, glass fiber post and composite core supported crown demonstrated significantly greater failure resistance than ferrule-containing endocrown preparations and standard endocrown in (premolar and molar teeth).