Effect of the Number of Residual Walls on Fracture Resistances, Failure Patterns, and Photoelasticity of Simulated Premolars Restored with or without Fiber-reinforced Composite Posts

IntroductionThis study compared the fracture resistances and the failure patterns of 100 simulated mandibular premolars of a different number of coronal walls (zero to four walls) with or without fiber-reinforced composite (FRC) posts. In addition, the photoelastic stress distribution was analyzed.MethodsThe fracture resistance was measured at a 45° angle with a crosshead speed of 1 mm/min, and the failure patterns were observed. The photoelastic stress distribution of specimens with or without FRC posts was also evaluated. The fracture resistance was analyzed by analysis of variance and a Duncan's multiple range test (p < 0.05).ResultsIn the no post groups, the fracture resistances decreased significantly in groups with two or fewer walls. The FRC post increased fracture resistances significantly, except for the zero-wall group, and optimized the failure patterns. A high stress concentration was observed along the canal space in the no post groups; stress seemed to be distributed in post groups in photoelasticity.ConclusionWithin the limitation of the experimental methods of this study, the FRC post was advantageous in lower premolars, especially with two or more walls in terms of the fracture resistance and stress distribution.