Pulp Response to Cavity Drying in Rat Teeth

¹ Naval Medical Research Institute. National Naval Medical Center, Bethesda, Maryland

The immediate response of the pulp was evaluated following drying of a cavity by a stream of temperate air for 5 minutes. Thirty-five maxillary first molar teeth, fifteen control and twenty experimental, were used. All cavity preparations were made under air-water spray with a wire-twist bur revolving at 1,300 + 40 rpm.

The following observations were made:

1. All twenty air-dried cavities showed odontoblast nuclei displacement into the dentinal tubules. Thirteen of fifteen non-airdried cavities did not show nuclei displacement into the tubules. This would seem to indicate that one immediate response of the pulp to the air-stream was displacement of the odontoblast nuclei into the dentinal tubules.

2. Within the dentinal tubules of the experimental teeth, vacuoles were seen within the displaced nuclei. These may be degenerative changes.

3. Increased number and depth of displaced nuclei occurred in tubules associated with the cavity margin, i. e., marginal displacement, in nine of twenty-two teeth.

4. A significant ( p < 0.01) correlation was found between the direct measurement of the cavity depth and both number ( r = 0.589) and depth ( r = 0.585) of nuclei displacement into the dentinal tubules.

5. The tubular measurement of remaining dentin was significantly correlated to the number ( r = -0.556, p < 0.02) and depth ( r = -0.456, p < 0.05) of nuclei displacement.

6. The direct measurement of remaining dentin was not significantly correlated to the number ( r = -0.403, p > 0.05) and depth ( r = -0.377, p > 0.10) of nuclei displacement.