The use of the replica technique to record fluid emerging from exposed dentine

The effect of pulpal cavity pressure on structures present on etched and unetched dentine was determined in 24 human premolars in vitro. The dentine was exposed in vivo. After extraction, the pulp was removed and the crown stored in 2.5 N sodium hydroxide for 3 days to remove the odontoblasts. The pulp cavity was filled with Ringer’s solution at atmospheric pressure, +30 or −5 mmHg. After 30 s–5 min a silicone-rubber impression was taken of the cavity floor and a resin cast prepared and examined in a SEM. The replicas reproduced the dentine surface accurately when there was no outward flow through dentine. With a pressure of + 30 mmHg in the pulp cavity, but not at the lower pressures, droplets were present on unetched dentine after 30 s. Droplets accumulated less rapidly on etched dentine, indicating that it may act as a sponge.