Effect of core∶dentin thickness ratio on the flexure strength of IPS Empress Ⅱ heat-pressed all-ceramic restorative material / 北京大学学报(医学版)

ABSTRACT

Objective: To evaluate the effect of core∶dentin thickness ratio on the flexure strength, fracture mode and origin of bilayered IPS Empress Ⅱceramic composite specimens. Methods: IPS EmpressⅡ core ceramic, dentin porcelain and bilayered composite specimens with core∶dentin thickness ratio of 2∶1 and 1∶1 were tested in three-point flexure strength. Mean strengths and standard deviations were determined. The optical microscopy was employed for identification of the fracture mode and origin. Results: The flexure strength of dentin porcelain was the smallest (62.7 MPa), and the strength of bilayered composite specimens was smaller than single-layered core ceramic(190.2 MPa). The core∶dentin ratio did not influence the strength of bilayered composite specimens. The frequency of occurrence of bilayered specimen delaminations was higher in the group of core∶dentin thickness ratio of 1∶1 than in the group of 2∶1. Conclusion: IPS Empress Ⅱcore ceramic was significantly stronger than veneering dentin porcelain. Core∶dentin thickness ratio could significantly influence the fracture mode and origin, and bilayered IPS Empress Ⅱceramic composite specimens showed little influence in the fracture strength.