Dentin permeability and bond strengths after various surface treatments

Numerous reports suggest that removal of the smear layer increases the bond strengths of some dentin adhesives while lowering the bond strengths of others. Smear layer removal also increases dentin permeability and wetness. The purpose of this study was to compare the permeability and shear bond strengths of occlusal vs. buccal dentin before and after removal of the smear layer with 6% citric acid and before and after substitution of the smear layer by topical oxalate treatment. Shear bond strengths of Scotchbond/Silux to smear layers were higher than those to acid-etched dentin. Oxalate treatment of acid-etched dentin increased bond strengths to levels that were higher than smear layer controls. Removal of the smear layer increased dentin permeability. This result was completely reversed by oxalate treatment.