Adhesive bond strength and compliance for denture soft lining materials.

Peel bond strength and tensile bond strength between three polyvinylsiloxane denture soft liners and a heat-cured acrylic resin denture base were measured using two adhesive systems. The soft lining materials differed only in regard of their filler content and compliance. The values of bond strength and mode of failure were explained in terms of the inherent strength of the bond and varying compliance and tear strength of the soft material. For tensile testing, when bond failure occurred through an adhesive debonding mechanism, materials of low compliance (stiffer materials) produced the greatest tensile bond strength. Conversely, when the same materials were subjected to peel testing a different trend emerged; the material with lowest compliance produced the lowest peel bond strength. When de-bonding occurs by tearing or snapping of the soft material, the measured value of bond strength was controlled by the tear strength of the soft material. The results could be explained by a consideration of stress concentrations at the soft-hard material interface during 180 degrees peel testing. Adhesives based on ethyl acetate solvents produced stronger bond strengths than equivalent toluene based adhesives, particularly for materials of low compliance. Bond failure for toluene based adhesives was predominantly adhesive, whereas that for ethyl acetate based adhesives was predominantly cohesive. Overall, the least resistance to peeling was exhibited by a material of low compliance (i.e. relatively stiff) bonded with a toluene based adhesive. When an ethyl acetate based adhesive was used, all materials exhibited a resistance to peeling with a predominantly cohesive mode of failure.