and Aim: Different methods and materials are available for post and core (P&C) fabrication. We aimed to compare the fracture resistance and failure modes of endodontically treated maxillary central incisors restored with six different P&C systems. Materials and Methods: In this in-vitro study, after endodontic treatment and coronal preparation of 60 maxillary central incisors, six different P&C systems were used: 1) cast base metal P&C, 2) cast gold alloy P&C, 3) zirconia post and casting

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... c core, 4) zirconia post and composite core, 5) titanium post and composite core, and 6) fiber post and composite core. Thermocycling (5-55°C, 60 seconds, 1500 cycles) was performed after cementing the full metal crowns on each tooth. A 130° force was applied at a crosshead speed of 1.5 mm/minute in a universal testing machine. The fracture force (N) and fracture patterns were recorded. Data were statistically analyzed by using Kruskal-Wallis, Mann-U-Whitney, and Fisher's exact tests (α=0.05). Results: The highest mean fracture resistance was recorded in the first group (904±302.77 N) followed by the third group (725±202.11 N), second group (723±224.15 N), fourth group (675±358.64 N), fifth group (424±156.85 N), and sixth group (416.5±81.58 N). The groups with casting P&Cs and zirconia post and casting core showed significant differences with the other two groups with non-casting cores (P<0.001). Conclusion: The highest fracture resistance was recorded for cast metal P&C, which may be due to a better stress distribution. Zirconia post and ceramic core may be a proper and aesthetically appealing substitute for cast metal P&C.