Introduction: Unlike interfacial bond evaluation methods such as the peel, tension, bending and shear tests with their dependence on the size of initiating cracks and subsequent lack of reproducibility, the chevron-notched short-bar test is more precise and reliable and it ensures interfacial crack initiation. Objective: To determine the interfacial fracture toughness of veneer and core ceramic-ceramic bonded bilayers using chevron-notched short-bar specimens. Materials and methods: T-shaped short-bar specimens (11mm x 6mm x 6mm) were fabricated from lithia-disilicate glass-ceramic (e.max Press) and the matched veneer (e.max Ceram) (n=16 each) according to the manufacturer's (Ivoclar Vivadent, Liechtenstein) recommendations.  The specimens were divided into two groups for veneering, Group 1 (core-veneer) and Group 2 (veneer-veneer). Group 1 core surfaces were covered with palladium foil prior to veneering, exposing only the chevron-notch. The thickness of the veneer was determined using E₁d₁³ = E₂d₂³ where E and d represent elastic modulus and thickness, respectively (Mecholsky and Barker 1984). Specimens were sintered in a programmable furnace (Programat-P80, Ivoclar). Group 2 specimens were prepared in the same manner.  Completed specimens were immersed in distilled water (37°C) for 30 days.  Specimens were loaded in a universal-testing-machine until fracture using a crosshead speed of 0.03mm/min to promote stable crack growth. The veneer-veneer results were used to calculate a constant. Results: The mean load-to-failure for veneer-core and veneer-veneer specimens were 38±11N and 41±7N, respectively. T-tests showed that there was no statistically significant difference between the two groups (p>0.05). The resulting value of interfacial fracture toughness for the core-veneer was 0.67MPa·m^1/2. Conclusion: The high stress concentration point at the chevron-notch initiates a stable, sharp crack at the interface. Thus, there is no need to pre-crack specimens or to measure crack length. This method shows promise as a reliable test for interfacial fracture toughness. Supported by NIH/NIDCR Grant DE06672.

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