Interaction between the dentinal smear layer and composite bond strength.

Freshly extracted human molars were used to study the interaction between dentinal smear layer removal with various agents, a dentinal adhesive, and the shear bond strength of a posterior composite resin to dentin. The use of Scotchbond dentinal adhesive in conjunction with the composite P-30, with the smear layer intact, produced the highest shear bond strengths. Removal of the smear layer produced bond strengths similar to those obtained with the smear layer intact. Application of ferric oxalate, and to a lesser degree 17% EDTA, resulted in diminished bond strengths. It was concluded that optimal bond strengths with the adhesive-composite resin systems tested may be obtained with an intact smear layer.