Adhesive bonding of various materials to hard tooth tissues--solubility of dentinal smear layer in dilute acid buffers.

While the acid etch technique has largely solved the problem of bonding restorative materials to enamel, attempts to improve adhesive bonding to dentin have so far had only limited success. One aspect to which insufficient attention has been paid is the presence of a smear layer on cut surfaces and of pellicle on surfaces exposed to saliva, both of which would reduce or prevent durable adhesive bonds. The present study attempts to evaluate the usefulness of various acidic solutions in removing these surface layers while causing minimal damage to the vital contents of the dentinal tubules. A series of twelve 0.16 M buffer solutions were applied to cut dentin surfaces which were then washed, dried and sputter-coated with gold/palladium in preparation for examination by scanning electron microscopy. It is concluded that the smear layer on cut dentin surfaces can be substantially removed in vitro by a 30 second exposure to an isotonic solution of buffered monobasic acids having pKa values between 3.8 and 2.5. Since these solutions did not always remove material from grooves in the prepared surface clinical techniques should aim at producing a smooth cut surface. The response of the vital pulp to this treatment still awaits investigation.