The effects of acid etching on the in-vivo permeability of dentine in the dog.

Cavities were cut in both lower molars of 11 anaesthetized dogs. Dentine permeability was quantitated in these teeth using a filtration technique before and after acid etching to remove the smear layer. Acid-etching increased 5-fold the ease with which fluid could flow across dentine. Under conditions of high fluid filtration, an opening into the pulp chamber from the opposite side of the tooth produced only slight increases in filtration rate, indicating that the rate-limiting step is filtration of fluid across dentine, rather than removal of the fluid by the pulp circulation.