Effect of dentinal fluid on enamel permeability under simulated pulpal pressure

To determine the effect of pulpal perfusion on the fluid flow through human tooth after different treatments at the enamel surface. Changes in mineral density along with fluid flow rate were also analyzed before and after etching.

The experiments were carried out on 97 human premolars. Ringer's solution and distilled water (DW) were applied under pressure of 20 mm Hg to the pulpal cavity of tooth crowns in the Ringer's-perfused and water-perfused groups respectively. Fluid flow through each specimen was recorded before and 0, 30, 60, 180 min after treatments at the enamel surface. The treatments included DW, 0.2% sodium fluoride solution, 1.23% acidulated phosphate fluoride gel (APF), 2.26% fluoride varnish (FV), 37% phosphoric acid gel (Etch) and artificial saliva (AS). Mineral density of the enamel was evaluated using micro-computed tomography.

In water-perfused group, fluid flow rates recorded after etching were significantly increased (p = 0.005) with the significant reduction of mineral density (p = 0.018) from baseline. A significant negative correlation was found (r = -0.78, p = 0.015). After FV, the percentage reduction from baseline was significant at 180 min (p = 0.003). In Ringer's-perfused group, etching immediately produced the greatest mean flow rate and subsequently returned to the baseline within 60 min after treatment (p < 0.001). There were approximately 40, 55, and 63% reductions of flow rates within 60 min after AS, APF and FV respectively.

Under simulated pulpal pressure, enamel fluid involves the process of enamel remineralization, particularly after etching.