Interfacial failure of a dental cement composite bonded to glass substrates

Objectives: To measure the interfacial fracture toughness and investigate failure mechanisms of dental cements bound to soda-lime glasses elastically equivalent to dental ceramics, as loading angle changes from 0 to 20°. Methods: Two half-circle glass discs received surface treatment were bound using dental cement (3M RelyXTM ARC BLBL) to make Brazil-nut sandwich specimens for interfacial toughness testing. Before bonding the two half-circle glass disks, 8% hydrofluoric acid (HF) was applied on the surfaces to bond for 2 min, washed thoroughly for 1 min under tap water and air dried. The surfaces were further treated using silane primer Monobond-s (Vivadent, Liechtenstein) for 60 s and air dried. Interfacial toughness as a function of mode mixity was measured using an Instron testing machine by changing loading angels from 0 to 20°. The interfacial fracture surfaces were examined using SEM and EDX to determine the failure modes when loading angles change. Results: Interfacial toughness increases from ∼1 to 8 J/m/m when loading angle increases from 0 to ∼20°. Increasing deformation and fracture in dental cement occur when loading angle increases. Significances: Increasing interfacial toughness can be attributed to more deformation and fracture of dental cement when loading angle increases. Brazil-nut sandwich samples are shown to provide a promising alternative method to evaluate bond strength and interfacial failure for dental restoration. Research was supported by NIH (NYU/PHS No. F5262-07).