Application of ethanol improves the resin-dentin bond strength of a two-bottle, self-etching primer-adhesive

To investigate whether the application of ethanol to a two-step self-etching adhesive can improve its resin-dentin bond performance.

Four different ethanol concentrations were added to the adhesive of Clearfil SE Bond to create four ethanol primers (40, 60, 80 or 100% ethanol). 24 extracted third molars were divided into four groups. Each group corresponded to one of the four hydrophobic ethanol primer concentrations. The teeth in the control group were bonded with Clearfil SE Bond according to the manufacturer's instructions. The primed teeth in the experimental groups were treated with the ethanol primer prior to application of the solvent-free adhesive. Microtensile bond strengths (mTBS) were tested 24 hours after specimen preparation. Another 14 teeth were bonded using the same methods to evaluate mTBS after 1 year. Nanoleakage was evaluated under field-emission scanning electron microscopy before and after aging.

In the 24-hour group, the mTBS in the 60% ethanol/40% adhesive primer group increased significantly (21.6%, P < 0.05) over the no ethanol control. After 12-month water storage, the bond strength of that experimental group was still higher than that of the control group (19.5%, P < 0.05). Before aging, the nanoleakage was clearly seen in the control group but hardly any was seen in the experimental group. After aging, the nanoleakage increase in the experimental group was much less than that in the control group.