Methods: Ten Metallic master dies were duplicated from prepared mandibular first molar teeth using a non-precious metal alloy NNB ( Sankin-Dentsply, Germany). In the next step 10 zirconia Standard copings with uniform thickness of 0.5mm and ten customized copings were fabricated by Cercon CAD/CAM system with the following features: 1 mm high labial reinforcing collar and 2 mm high lingual buttressing shoulder. Thereafter, these 20 Zirconia copings were veneered by an experienced technician using an index. All samples were then cemented onto the respected master metallic dies by Resin cement (Panavia F) under a static load of 25N. The samples were then placed into Universal Testing Machines (Zwick, Ulm, Germany) and underwent a vertical load at a crosshead speed of 0.5mm/min. The load was recorded when catastrophic fracture occurred. Data analysis were performed by Two-way ANOVA and t-Test.
Reults: Results of the present study showed the following mean loads at fracture: 1852.11± 587.9N for crowns with standard core designs and 3332.63± 916.38N for the customized group. Data analysis showed that the amount of Fracture load achieved in the group with Customized core design was significantly greater than the samples with standard designing (p< 0.0001).
Conclusion: Considering the limitations of this study, the customized core design showed higher results in fracture load testing in comparison with the standard group.
Keywords: Fracture, Zirconia Core, All-ceramic crown.