Abstract
Background: Fracture of restored endodontically treated teeth is a common complication. The mechanical properties of post systems may play a role in the incidence of tooth fracture. Aim: The purpose of this study was to evaluate in vitro the fracture resistance and pattern of fracture of endodontically treated teeth restored with three different post systems. Material and methods: Posts used were fiber-reinforced composite resin posts (FRC post), custom cast silver-palladium, and nickel-chromium posts and cores. A 3-point bending test was performed to calculate flexural strengths and elastic moduli of the specimens. Sixty extracted human maxillary canines were endodontically treated and divided into three groups (n = 20). All-ceramic crowns were fabricated and cemented with Variolink II resin cement. Ten specimens of each group were subjected to a constantly increasing load until fracture. The other 10 specimens were fatigued for 106 cycles in a custom-made fatigue machine. Recorded failure loads and modes were statistically compared with one-way ANOVA and Tukey-HSD tests (a = 0.05). Results: The resistance to fracture of teeth restored with FRC posts, composite resin cores, and Empress II crowns was similar to that of teeth restored with cast posts and cores (P = 0.162). Supracrestal (above root/level of acrylic resin base) oblique fracture was the predominant mode of fracture associated with teeth restored with FRC posts (70%), while vertical root fractures were more common with teeth restored with cast posts and cores. Conclusions: Teeth restored with the FRC post system did not exhibit vertical root fractures and were less likely to show root fracture. Sixty to 80% of teeth restored with both types of cast posts and cores showed vertical and subcrestal root fractures.