Relationship between the electrical resistivity of enamel and the relative humidity

The present study was carried out to investigate the relationship between the relative humidity and the electrical resistivity of enamel in vitro. The electrical resistivity of enamel samples was measured in a thermo-hygrostat where the relative humidity varied between 60% and 90%, with the measurements carried out first in a descending direction and then in an ascending direction. When the electrical resistivity was measured from a low to high relative humidity in an ascending direction, a higher value of electrical resistivity was always obtained in comparison to that when measured in the reverse descending direction. The difference between the mean electrical resistivity in an ascending and a descending direction increased in proportion to the relative humidity. These findings suggest that the diffusion of electrolytes and water in enamel is sensitive to changes in the relative humidity.