In vivo and in vitro study of enamel fluid flow in human premolars

Abstract

Objective: To investigate fluid flow through enamel in intact human premolars in vivo and in vitro by using the replica technique. Design: The experiments were done on 17 premolars of 10 subjects (aged 10–25 yrs) to be extracted during orthodontic treatment. Teeth were divided into 2 groups. In the first group (n = 11), the fluid accumulated on the enamel surface was recorded with the impression material in the mid-buccal enamel both in vivo and in vitro. In vitro replicas were obtained when the pressure in the pulp cavity held at 0, +20, +100, and +200 mmHg. They were examined by a scanning electron microscope (SEM). For the second group (n = 10), each tooth was prepared for fluid flow measurement during which the pulpal pressures of +20, +100, +200, and +300 mmHg were applied. Results: The mean number of droplets presented after the pressure had been raised to 200 mmHg is significantly greater than those observed at lower pressures, including those obtained from the same tooth in vivo. A significant linear relationship between these numbers and the pulpal pressures was found (p < 0.001). In vitro fluid conductance through the crown also increased significantly with increased pressure (p < 0.001). Conclusion: SEM evaluation of droplets distribution on enamel surface revealed that the presence of fluid transudation forced by pulpal pressure may influence the accumulation of enamel fluid on the tooth surface in vitro, similar to those observed in vivo. © 2020 Elsevier Ltd