The effect of fiber bundle posts used with different core materials on fracture resistance

Aim: The aim of this study is to evaluate the effect of using fiber bundle post and conventional fiber post with different core materials on fracture resistance through comparative analysis. Method: In the study, 60 single-rooted and single-canal upper incisors were used. Root lengths were 15±0.5 mm in length and were removed by cutting at the enamel cementum junction. After determining the working length, a biomechanical preparation was performed to achieve an apical dimension of #35.04, and the canals were filled with #35.04 gutta percha. The post space preperation was achieved by utilising a Gates Glidden bur #3, ensuring a 5 mm remnant of gutta-percha was retained in the apical region of the root. The specimens were randomly divided into two main groups according to the type of post to be used: fiber posts and fiber bundle posts (N=26). Each main group was further subdivided into two subgroups (n = 13) according to the core material to be used: a condensable microhybrid composite or a flowable microhybrid composite included in the fiber bundle post kit. The posts were cemented with a dual cure self-etch resin cement, afterwards the core buildups were fabricated. The samples were placed in acrylic blocks. A universal testing machine was used to apply force to the samples at a cross head speed of 1 mm/min to perform the fracture test. Result: No statistically significant difference in fracture resistance was found between the restorations using fiber posts and those using fiber bundle posts with different core materials (p > 0.05). However, when the core material type was evaluated, specimens restored with a condensable microhybrid composite core exhibited significantly higher fracture resistance compared to those restored with a flowable composite (p < 0.05). Conclusion: While no difference in fracture resistance was observed between fiber or fiber bundle posts restored with condensable and flowable microhybrid composites, it was found that the fracture resistance of condensable composite core structures supported by fiber posts and bundle posts was higher in the fiber bundle post group. Consequently, it is believed that the use of fiber bundle posts with condensable microhybrid composites will contribute positively to the fracture resistance of teeth.