Effect of primer dwell time on dentin bond strength

The period of time that primers are to be applied to etched dentin surfaces is sometimes clear and sometimes not indicated in the instructions accompanying the bonding system. In this study, primers with either alcohol or acetone solvents appeared to act rapidly and not show any significant improvement with extended primer dwell time. When resin adhesive primer application periods were prolonged, significant improvements in the bond strengths of some adhesives occurred. Water-based primers placed on dried etched dentin surfaces appear to require longer application times than do acetone or alcohol-based primers applied to wet etched dentin surfaces. Careful attention is required regarding the application of these materials. If in doubt about the primer application, longer primer application periods should be used.