Observations on fluid flow from exposed dentine in primary teeth: An in vitro study.

Objective: To investigate fluid flow through dentine in primary teeth in vitro using the replica technique, and to compare the results with those obtained from permanent dentine.

Design: The experiments were carried out on 22 extracted, mandibular, primary, incisor teeth. The incisal edge was removed to 1mm below the dentino-enamel junction and half the exposed surface etched with phosphoric acid. The exposed dentine was blotted dry and the pressure in the pulp cavity held at 0, 15, 30 or 45cm HO above atmospheric for 30s. Fluid that accumulated on the dentine surface was recorded with impression material and a replica made with epoxy resin which was examined in a scanning electron microscope.

Results: Structures resembling fluid droplets were present in the replicas of unetched dentine in all 22 teeth, and at all the pulpal pressures tested. The droplets formed at 45cm HO were significantly larger (median diam., 5.14mm; interquartile range, 3.26mm; Friedman repeated measures analysis of variance on ranks (RMAVR) and Tukey test) than those formed at other pressures. There was no evidence of droplets in the replicas of etched dentine with any of the pulpal pressures.

Conclusions: These results demonstrate that fluid will tend to flow from dentine in deciduous teeth when it is exposed. They are similar to those obtained in a previous study in this laboratory on permanent teeth. The fact that fluid droplets were absent from etched dentine suggests that, after being blotted, the etched dentine matrix absorbed fluid that tended to flow out through the dentinal tubules.