Calculation models for average stress and plastic deformation zone size of bonding area in dentine bonding systems.

Average stress during shear bond testing, and deformation behaviour during nano-indentation testing were calculated for the bonding area as a bonding site for copolymerization with resin composite in dentine bonding systems. First average stress was calculated in the bonding area between bovine dentine and composite resin. Secondly, the plastic deformation zone size was calculated using an elastic/plastic deformation zone model after a nano-indentation test. The result clearly showed that average stress depended upon the elasticity of the bonding area, the elasticity value ratio of the composite resin-to-bonding area, and interfacial stress between the dentine and the adhesive resin. In this bonding area, the elasticity/hardness ratio changed depending on the thickness of the bonding area as well as the plastic deformation zone size (b), expressed as a (b/2a)-value (indented triangular length (2a) at nano-indentation test) expanded with increasing the elasticity value.