Relationship between the electrical resistivity of enamel and the relativehumidity

The present study was carried out to investigate the relationship between t he relative humidity and the electrical resistivity of enamel in vitro. The electrical resistivity of enamel samples was measured in a thermo-hygrosta t where the relative humidity varied between 60% and 90%, with the measurem ents carried out first in a descending direction and then in an ascending d irection. When the electrical resistivity was measured from a low to high r elative humidity in an ascending direction, a higher value of electrical re sistivity was always obtained in comparison to that when measured in the re verse descending direction. The difference between the mean electrical resi stivity in an ascending and a descending direction increased in proportion to the relative humidity. These findings suggest that the diffusion of elec trolytes and water in enamel is sensitive to changes in the relative humidi ty.