In situ observation on the failure behavior of ZrO2-resin-dentin bonding interface with prefabricated indentation defects

Abstract

Interfacial cracking and fracture of restorative materials are major obstacles to realize effective dental restoration. Especially, the bonding failure of compound interfaces consisting of dentin, resin and zirconium dioxide (ZrO2) ceramic, exhibit complexity, variability and unpredictability due to the complicated loading type and oral environment. By using a self-developed miniaturized horizontal device integrating with thermostatic artificial saliva, an approximate oral environment was established to investigate the failure mechanism of ZrO2-resin-dentin compound interfaces. Through real-time in situ observation of shearing deformation behaviors of the dentin-resin and resin-ZrO2 interfaces, the continuous propagation processes of cracks nucleating from the interfacial intersection line or dentin's interior were analyzed in detail. The discontinuous cracking behaviors revealed the prior crack of resin-ZrO2 interface, which attributed to the acid etching of dentin and significant gradients in Young's modulus and hardness compared with the corresponding parameters of dentin-resin interface. The significant interfacial differences in mechanical properties promoted the crack nucleation and induced the bonding failure. A widest crack with a width of 1.4 μm inside the dentin was also observed from the fractured ZrO2-resin-dentin specimen. This paper focused on the discontinuous interfacial cracking behaviors and bonding failure mechanisms of ZrO2-resin-dentin specimen, which would be beneficial to the research of novel composite resins and the improvement of bonding processes.