الفهرس 
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Abstract
Objective: The aim of this study was to compare the fracture resistance of different aesthetic core materials supported by two different non-metallic posts covered with ceramic crowns. Material and methods: Thirty intact maxillary central incisors were selected. The crowns were decoronated 2mm coronal to the most apical point of the labial CEJ. After root canal therapy, standardized preparation of the coronal portion of the teeth was done using a milling machine. These teeth were divided in to two groups according to the type of tested post. Group 1: (n=10) teeth were restored with glass fiber post (Exacto). Group 2: (n=15) teeth restored with zirconia post (CosmoPost). Each group was further divided into sub-groups of 5 samples each according to the type of core build-up materials: Group 1: Sub-group A: Ready-made glass fiber core (Reforcore), Sub-group B: Composite core material (Core-X Flow). Group 2: Sub-group A: Ceramic core (Cosmo-Ingot), Sub-group B: Ready-made glass fiber core (Reforcore), Sub-group C: Composite core material (Core-X Flow). All teeth were restored with IPS e-max II ceramic crowns. A control group of five intact maxillary central incisors were added to the study. All samples were subjected to thermocycling in a Thermocycling Machine and fracture resistance test using a Universal Testing Machine. Failure loads were measured under a static loading test using the machine with a load-cell of 5kN and data were recorded and statistically analyzed. Results: The difference in fracture resistance between both posts (Glass fiber post and Zirconia post) with Glass fiber core was statistically non-significant, while with composite core was statistically significant. Regardless to core material, it was found that the total Glass fiber post group recorded the highest fracture resistance mean value (510.1976 N) followed by control group (467.7374 N), while total Zirconia post group recorded the lowest fracture resistance mean value (398.3282 N); the difference between groups was statistically non-significant. On the other hand, regardless to post type, it was found that total Glass fiber core recorded the highest fracture resistance mean value (471.2226 N) followed by control group (467.7374 N) then total Composite core (450.055 N), while total Ceramic core recorded the lowest mean value (432.1763 N), the differences between groups was statistically non-significant. Conclusion: There was no improvement in the fracture resistance of the aesthetic post systems when used with the most recently introduced fiber reinforced core (Reforcore