Microtensile bond strength of different components of core veneered all-ceramic restorations - Part II: Zirconia veneering ceramics

Objectives. The purpose of this research was to investigate microtensile bond strength between one type of zirconia substrate and various commercial veneer ceramics. The effect of an optional liner material between the core and veneer was also evaluated where applicable. Methods. Bilayered zirconia veneer discs were fabricated from five layering and two pressable veneer ceramics. Additionally, discs from each veneer ceramic were prepared. The discs were cut into microbars of 6 mm in length and 1 mm in cross-section. The microtensile bond strength was tested in a universal testing machine. The fracture surfaces of the microbars were examined with scanning electron microscopy (SEM) and EDAX. Results. The microtensile strength of Rondo Dentine and Lava Dentine veneer ceramics were significantly higher than the other tested veneer ceramics. Furthermore, the layered systems Rondo Dentine and Ceram Express were significantly stronger than the other tested core-veneer ceramics. The application of liner material dramatically affected the bond strength and failure mode, which was also material dependent. SEM analysis showed that two pressable veneers and one type of layering veneer ceramic failed entirely cohesively in veneer side while the remaining test groups had higher percentage of interfacial failure. Significance. Selection of stronger veneer ceramics which have good bond strength with zirconia can reduce the chances of chipping and delamination under function. The liner material should only be used with some layering veneers but not in combination with pressable veneers as it will result in weakening of the microtensile bond strength. (C) 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.