Effect of adhesive layer thickness on the bond strength of a zinc polycarboxylate dental cement

This study reports the effect of varying the thickness of a commercial zinc polycarboxylate dental cement on its adhesion in a metal-to-metal single lap joint. The thickness was controlled externally in a specially designed apparatus, rather than by the inclusion of isodimensional glass spheres, as has been done previously. The results show that both the tensile shear bond strength and the mode of failure of the cement are influenced by the thickness of the cement layer in the bonded joints. Hence, these results confirm previous findings that there is an optimum thickness for the zinc polycarboxylate layer. They also show that failure is more likely to be cohesive with thicker layers.