the retention and fracture resistance of two all-ceramic post and core systems in anterior endodontically treated teeth

background : in anterior endodontically treated teeth a better esthetic can be achieved by using all-ceramic post -core restorations instead of metal post systems. maximum retention and fracture resistance of the post are the criteria upon which selection of a post system is based. the aim of this study was to evaluate the fracture resistance and retention of two all-ceramic post and core systems including ips empress 2 post-core system and ips empress 2 core connected to zirconium cosmopost, and comparing these features among the two groups material and methods :  eighty extracted maxillary central incisors and canines were divided into two groups of 40 including ips empress 2 and zirconium cosmopost. to evaluate retention, shear force was applied to the cement at the crosshead speed of 0.5 mm/min; force was applied until the post was detached from the canal.  to measure the fracture resistance, the samples were loaded at 45-degrees to the horizon at the crosshead speed of 5 mm/min until fracture occurred. result : the mean fracture strength and standard deviation of zirconium cosmopost and ips empress 2 were 302.10 n (69.922), 151.63 n (48.661), respectively. the difference between groups was significant statistically (p<0.001). the zirconium cosmoposts had lower retention than ips empress2 dowel-core, but the difference between groups was insignificant (p =0.134).   conclusion :  within the limitations of the study, it could be concluded that zirconium cosmopost system may be a candidate for the restoration of anterior endodontically treated teeth, as the high fracture toughness and propitious esthetic feature.