Clarkson B H, Wefel J S, Feagin F F
J Dent Res. 1986 Jul;65(7):963-6. doi: 10.1177/00220345860650071301.
Using a microdissection technique to obtain samples from carious and adjacent sound enamel, we compared the fluoride concentrations in surface and subsurface enamel. Undialyzed and dialyzed gels were used to create lesions with and without negatively birefringent surface zones, respectively. The fluoride concentration in the surface enamel of the lesions was always greater than that in the corresponding sound enamel, as was the subsurface fluoride concentrations of caries lesions compared with adjacent sound enamel at the same depth.