Birefringence and mineral content of the first stage of artificial carious lesion formation (a combined polarizing microscopic, microradiographic and scanning electron microscopic investigation).

Artificial carious lesions were made using acetic buffer solutions of pH 6.0 containing calcium and phosphate. The solutions were highly undersaturated with respect to hydroxyapatite. Out of 72 lesions 51 showed subsurface demineralization, whereas in 21 only a superficial demineralization occurred. These superficial lesions were examined using polarized light microscopy, microradiography and scanning electron microscopy. This superficial breakdown of enamel material, considered as the initial demineralization of the enamel, appeared to occur at the prism junctions. This was indicated by the polarizing microscope technique and was made clearly visible using scanning electron microscopy. Quantitative polarizing microscopy and microradiography revealed results which correlated very well. From this it is probable that the initial superficial demineralization of the enamel is--under the described conditions--a simple dissolution reaction.