Abstract: Objective: To explore the optimal design of the framework so that to improve the fracture strength of the zirconia crown. Methods: Four different framework designs based on the thickness of zirconia cervical collar were used: 0.00mm zirconia collar(Group A), 1.00mm (Group B), 2.00mm (Group C), and height of contour(Group D).There were 7 samples in each group. The universal test machine was used to test the fracture load. The damage shape was observed by the body type microscope and scanning electron micrographs. Results: Mean of fracture loads were 1.56KN for Group A, 1.83KN for Group B, 1.95KN for Group C, and 2.27KN for Group D. The fracture load of four groups showed a significant difference. Group A was significantly different from Group D. Damage shapes were crack and chipping. There was no significant difference in the composition ratio between four sets of damage shapes. Conclusion: The framework design can affect the fracture strength of the zirconia crown, and the more thick of zirconia collar, the higher fracture strength of zirconia crown.

Key words: Zirconia, Tooth crown, Cervical collar, Fracture strength