Evaluation of a one-piece milled zirconia post and core with different post-and-core systems: An in vitro study

One-piece milled zirconia posts and cores present an esthetic option as foundation restorations for ceramic crowns. To date, dimensional fit and load capacity of 1-piece zirconia posts and cores have not been determined. The purpose of this study was to evaluate the accuracy of fit of milled zirconia posts and cores and to compare the shear strength with other post-and-core systems. Eighty-five maxillary central incisors and canines received endodontic treatment and were divided into 5 groups (n=17) as follows: cast gold post and core (Au) as control, 1-piece milled zirconia post and core (Zr), prefabricated zirconia post with heat-pressed ceramic core (Zr/Cer), titanium post and composite resin core (Ti), and combined fiber/zirconia post with composite resin core (Fiber/Zr). The posts and cores were cemented with dual-polymerized composite resin cement (Multilink). Zirconia copings were made for each specimen, cemented, and loaded to failure. Fracture loads and modes of failure were recorded. Fracture loads were compared with a linear model. Differences in the mean marginal gap distance between the post-and-core patterns and the adjusted milled zirconia posts and cores were analyzed with a paired t test (α=.05). A significant difference was found in the marginal gap distance of group Zr (P<.001), compared with the marginal gap distance of the acrylic resin patterns. Mean loads to failure were highest for the Fiber/Zr group in comparison with custom-made milled zirconia posts and cores (P<.001). All systems evaluated presented sufficient mean load-to-failure values for anterior tooth restorations, including the recently developed 1-piece milled zirconia post and core.