Evaluation of the bond strength of circular and oval posts luted in oval shaped canals

Aim. The aim of this laboratory study was to evaluate the post-root dentin push-out strength of circular and oval posts luted in oval shaped canals with two different resin cement. Methods. Twenty monoradicular premolars with oval-shaped canals were selected, endodontically instrumented and obturated. The teeth were divided into two groups according to the drill – fiber post system used for the preparation of post-space (Ellipson oval tip+post and MTwoPF+DT light post). Each group was subdivided into two subgroups according to the cement used (Core and Gradia Corecem Automix). The bond strength was evaluated with thin-slice push-out test. The bonded area was calculated with an appropriate geometric formula in order to express the retentive strength of the post segment in MPa. The results were analyzed by Kruskal-Wallis ANOVA. Results. The results revealed that neither the drill-post system nor the cement significantly affected the push-out bond strength. Conclusions. In terms of bond strength, Ellipson system resulted as effective as a circular drill-post system. Nevertheless the use of the oval tip-oval system has some advantages. The thickness of the resin cement may be a critical factor for the clinical performance of the fiber posts: as an excessively thick layer of resin cement around a fiber post was correlated to higher frequencies of post debonding. The oval tip-post system could overcome this inconvenient.