Diffusion through bovine tooth enamel as related to the water structure in its pores

Abstract

Diffusion coefficients of 86Rb +, 36Cl −, [ 3H]-sorbitol and [ 14C]-glycerol through enamel were determined both in the absence and the presence of urea or t-butanol which are known for their structure-breaking and structure-promoting properties respectively in aqueous solutions. Their effect on the diffusion coefficients could be explained solely on the basis of the respective shifts in the relative viscosities of the aqueous solutions, indicating that the water of the transport phase is probably free water, in accord with explanation for the extra increase of diffusion coefficients with temperature (Burke and Moreno, Archs oral Biol. 17, 433–437 (1975)) by the hypothesis that the amount of free water increases with temperature at the expense of bound water.