Interfacial failure of a dental cement composite bonded to glass substrates

Summary 

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 2min, washed thoroughly for 1min under tap water and air dried. The surfaces were further treated using silane primer Monobond-s (Vivadent, Liechtenstein) for 60s 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 8J/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).

Keywords: Fracture, Interfacial fracture toughness, Dental cement, Glass, Ceramic crowns, Fracture mechanisms