Influence of pressure application before light-curing on the bond strength of adhesive systems to dentin

This study evaluated the influence of defined pressure application before light-curing on the tensile bond strength (TBS) of two adhesive systems to wet and perfused dentin. Bonding sites were analyzed by scanning electron microscopy (SEM) to assess morphological changes. Dentin discs from 120 human third molars were prepared in such a way to allow simulation of intrapulpal pressure. The specimens were randomly assigned to 6 groups (n=20) according to different experimental conditions. The adhesive systems (ScotchbondTM Multi-Purpose and Syntac(R)) were applied either to wet or perfused dentin. In the latter, compression was applied before adhesive light-curing . TBS was recorded using an universal testing machine. Qualitative examination of the bonding sites was performed by SEM after dissolving the dentin with 50% nitric acid. Pressure application prior to light-curing resulted in a remarkable decrease of TBS for Syntac(R), while no significant change was observed for ScotchbondTM MP. SEM analysis showed no considerable lengthening of the resin tags after pressure application. These findings suggest that application of adhesive systems to dentin under pressure before light-curing had no positive effect on TBS.