Introduction: The aim of this study was to compare the fracture resistance and fracture mode of the maxillary central incisors restored with four different post and core systems. Methods and Materials: Forty extracted Maxillary central incisors were selected. After root canal treatment, teeth were assigned to 4 groups (n=10). First group was restored with Gold alloy casting post & core as control group (GCPC), second group with zirconia post and heat pressed ceramic core (Zr/Cer), third group with zirconia post and composite core (Zr/Com) and fourth group with glass fiber post and composite core (GF/Com). Full metal crown prepared for each tooth and cemented with GI. After thermo cycling, compressive load was applied and fracture strength values and failure modes were evaluated. Data were analyzed by, one- away Anova and chi-square test (p<0/05). Results: The mean failure loads (N) were in this order: Zr/Cer group: 761±244/137, GCPC group: 728±283/198, Zr/Com group: 715±425/181, and GF/Com group: 444/9±97/724.The mean failure loads in GF/Com group was significantly lower than other groups (p =%001). The difference was not significant among other three groups. Concerning fracture mode, the highest percent of favorable fractures observed in the Zr/Cer group with six favorable fractures but there was no significant difference among studied groups (p=0/849). Conclusion: Central incisors restored with GF/Com represented significantly lower fracture resistance. There was not any significant difference in fracture modes of studied groups
