Fracture strength of endodontically treated teeth restored with FRC posts

Objectives: The aim of this study was to evaluate the fracture strength and the mode of failure of endodontically treated teeth restored with carbon-fiber and glass-fiber reinforced (FRC) posts in comparison to teeth restored with titanium posts. Methods: Thirty five endodontically treated human maxillary central incisors were divided into four groups. The first three groups (n=10) were restored with carbon-fiber (group A, Carbonite) and glass-fiber posts (group B, DentinPost and group C, ParaPost FiberWhite). Group D (control group, n=5) was restored with prefabricated titanium posts (ParaPost XP). Composite cores were built up in all teeth. Groups A to C were divided into two subgroups. One of the subgroups (A1-C1, n=5) was subjected to thermocycling (2000x, 5oC and 55oC, 3c/min). All the specimens were loaded until fracture at a 45o angle to the long axis employing 0,5 mm/min crosshead speed. Statistical analysis was performed by two-way ANOVA. The mode of failure was evaluated macroscopically. Results: Failure load (N): Group A: 421,2±42,1, group B: 342,3±43,9, group C: 296,5±50,9 and group D: 604,1±99,6. Statistically significant difference was found between group D and groups B and C. The thermocycled FRC subgroups (Group A1 372±60N, Group B1 248±70,1N, Group C1 217±76,5N) showed no statistical difference from the non-thermocycled ones or among them. Debonding of the core without post displacement was the main failure mode observed in groups B and C, whereas vertical root fractures were found in group D. Group A exhibited both modes of failure in similar percentages. Conclusion: The carbon fiber posts tested in this study exhibited similar fracture strength to titanium posts, while the glass fiber posts showed lower strength and non catastrophic failures. Thermocycling did not have any effect to the strength of FRC posts.