INTRODUCTION: This 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. METHODS: The fracture resistance was measured at a 45 degrees angle with a crosshead speed of 1mm/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). RESULTS: In 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. CONCLUSION: Within 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. Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.
INTRODUCTION: This 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. METHODS: The fracture resistance was measured at a 45 degrees angle with a crosshead speed of 1mm/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). RESULTS: In 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. CONCLUSION: Within 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. Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.