applied fracture mechanics

Fracture of Dental Materials 133induces shrinkage stresses between the tooth and the adhesive, as well as between theadhesive and the restorative material, does not make the situation manageable, which isfurther complicated by differences in mechanical/physical properties of the differentmaterials forming a joint. In the following section we will approach the adhesive joint in anattempt to identify different challenges associated with this region.When it comes to the failure mechanism at the dentin resin interface, there are certainquestions that need to be addressed. These questions include: (1) does failure at the humandentin-resin interface occur by a cohesive or an adhesive mechanism? (2) is the failuremechanism accompanied by a plastic deformation, and if so how important is it? To addressthese questions, Lin and Douglas [67] performed a computational analysis and fractographyof two different bonding systems: Scotchbond- (SB2) and Scotchbond-Multipurpose (SBM).The difference between these two systems is that SB2 consists of a mixture of primer and aso called bonding resin, while SBM uses the same primer and bonding resin, but in contrastto SB2 they are placed as separate systems on the dentin surface. According to theirestimates, the dentin-resin interracial fracture toughness (GIC), for the SB2 and for the SBMwere 30.22 ± 5.61 and 49.56 ± 7.65 J m -2 , respectively, which were significantly different (p