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The sensitivity of dentin. Changes in relation to conditions at exposed tubule apertures.

The sensitivity of experimentally exposed dentin, where the conditions at the outer tubule apertures were changed by various treatments, was studied in 40 contralateral pairs of teeth by intra-pair comparison. The results showed: (1) Dentin areas exposed by fracture were more sensitive than wet-ground dentin surfaces to application of dry, absorbent paper, scraping with a probe and a short blast of air. (2) Ground dentin surfaces treated for 2 minutes with 50% citric acid were more sensitive to the above mentioned stimuli and to application of a hyperosmotic solution (4-M CaCl2) than were untreated ground surfaces. (3) The sensitivity of ground dentin surfaces was markedly reduced by dehydration by a jet of air for 1 minute. The sensitivity rose after rehydration of the dehydrated surfaces by rubbing with water or gentle wet grinding. It is concluded that mechanical and dehydrating pain-producing stimuli are more readily transmitted from a dentin surface when the exposed tubule apertures are wide open, an...