In vitro evaporative vs. convective water flux across human dentin before and after conditioning and placement of glass-ionomer cements.

PURPOSE: To assess the convective and evaporative fluid movement across glass-ionomer treated dentin. METHODS: Crown segments made from extracted human teeth, were divided into two groups of 14 teeth each. Each segment was cemented onto a plexiglass slab penetrated by a stainless steel tube, permitting filling of the pulp chamber with water. This set-up was attached to a device that measured fluid movement through the dentin in the crown segment. The experimental design involved repeated measurements of convective and evaporative fluid movements in each of the following conditions: smear layer-covered dentin, conditioned dentin, dentin after placement of one of two glass-ionomers (Fuji IX or Ketac-Molar), with and without a protective coating. The same water fluxes were remeasured after storage of the samples for 24 hours in distilled water. RESULTS: Statistical analysis of the results using ANOVA indicated a significant difference between the two measured water fluxes (P < 0.001). There was also a significant difference between the two materials (P < 0.001), with Ketac-Molar allowing higher permeability than Fuji IX. Conditioning the dentin surface with polyacrylic acid increased the convective water flux (P < 0.05) but did not change the evaporative water flux. Placement of the glass-ionomer material did not change the rate of spontaneous evaporation of water from the dentin, but the application of a coating agent reduced the evaporative water loss. These values were not significantly different when the specimens were stored for 24 hours.