Modified procedure for the quantitative estimation of pore volumes in carious dental enamel by polarizing microscopy.

The polarizing microscope was used to make two estimates of pore-volume fraction in carious enamel. Estimates from form birefringence were always much lower than estimates from the intrinsic birefringence of the enamel solid and were too low for carious enamel. The discrepancy cannot be explained except in part as being due to re-precipitation of mineral during lesion formation. The discrepancy may arise largely from the unjustified assumption that the whole tissue acts as a Wiener composite body. Form birefringence is probably produced only by a fraction of the tissue. A model which reconciles the two pore-volume estimates and enables calculation of the composite body fraction and of the volume fractions of solid within this fraction and in the tissue as a whole is described. It appears that polarizing microscopy will require the conjoint application of other techniques for quantitative estimation of pore-volume fractions.