evaluation of retention of two different cast post-core systems and fracture resistance of the restored teeth

statement of the problem: the survival of pulpless teeth restored with different post and core systems is still a controversial issue. purpose: this study compared the retention of two different post and core systems and also the fracture resistance of teeth restored with these systems. material and method: eighty endodontically treated maxillary central incisors were sectioned perpendicular to the long axis at a point 2mm incisal to the cemento-enamel junction (cej) and then the root canals were obturated. the restored teeth were randomly divided into two equal groups of 40. one group was restored with nickel-chromium (ni-cr) post and core system and the other group with non-precious gold alloy (npg) system. for evaluation of fracture resistance of the restored teeth, the specimens (n=20 per each group) were mounted in acrylic resin blocks and a layer of polyvinyl siloxane was applied to cover the roots. loads were applied at an angle of 45 degrees to the long axis of the teeth and measured with a universal testing machine. the axial retention values of the studied groups (no=20) were measured on an instron testing machine at a crosshead speed of 0.5 mm/min. statistical analyses were performed using spss version 19.00 and student’s t-test (α=0.05). results: although retention failure load for ni-cr system was lower than npg system, there was no significant difference between the two systems ( p = 0.7). however, fracture resistance of the teeth restored with ni-cr post and core system was significantly higher than npg group ( p = 0.000). conclusion: there was no significant difference between the retention of the studied post and core systems. although significantly higher fracture thresholds were recorded for ni-cr post and core group, the failure loads of both systems may rarely occur clinically.