Fracture Resistance of Three Different Post and Core Systems on Endodontically Treated Teeth: An In Vitro Study

Background: Endodontically treated teeth are usually more susceptible to fracture because they have insufficient coronal tooth structure as a result of caries, trauma, or the endodontic procedure itself. Posts are recommended to strengthen weakened endodontically treated teeth against intraoral forces by distributing torquing forces along the roots. Currently, a wide variety of custom and prefabricated dowel systems are available to improve the retention of extra-coronal restorations of non-vital teeth. The objective of the study was to comparatively evaluate the fracture resistance and mode of failure of three types of dowel systems. Materials and Methods: A total of 30 premolars were used in this in vitro study. The crown portion was removed at 2 mm from the cemento-enamel junction was endodontically treated. The specimens were randomly assigned to three groups to receive cobalt chromium cast metal post, carbon post, and zirconium post. The roots were embedded in the acrylic block, and a load was applied at 90 to the occlusal surface until fracture, at a crosshead speed of 1 mm/min. The data were analyzed statistically with ANOVA with post-hoc Tukey honest significant difference. Results: Mean fracture resistance (KN) for cast post and core was highest with a mean value of 5.02 ± 0.32. The carbon post and zirconia post had a maximum load at failure of 1.67 ± 0.26 and 2.27 ± 0.23, respectively. The carbon fiber post and zirconium had a significantly lower strength than cast post and core. Conclusion: All the three systems exhibited fracture resistance that can withstand normal functioning of an endodontic dowel system. Carbon fiber post showed a modulus of elasticity similar to dentin and can be used in most cases. Zirconia prefabricated dowels can withstand higher load but can end up with root fracture. Hence, the selection of dowel system should be based on an individual case basis.