A Quantitative Microradiographic Study of Incipient Enamel Caries

¹ Karolinska Institutet, School of Dentistry, Stockholm, Sweden

Using quantitative Microradiographic technique the authors measured the mineral content in the enamel in 11 cases of incipient proximal caries in young individuals. In 9 cases the seemingly caries-resistant surface layer persisted. The mean value for its thickness was 40 µ, and for its mineral content, 82.7 per cent by volume. The latter figure indicated that the surface laver had lost approximately 8 per cent of its mineral salts in connection with the carious decalcification.

The mean value for the mineral content in the seemingly normal enamel situated between the deepest part of the carious lesion and the dentin was 87.2 per cent by volume. The degree of subsurface decalcification in the above-mentioned nine cases exhibited great variations, and no clearcut positive correlation could be found in the present, limited material between the depth of a carious lesion and the degree of decalcification. The lowest mineral content in the material, 28.9 per cent by volume, was thus found in a 300-µ-deep lesion, whereas the corresponding figure for a 600-µ-deep lesion was only 47.0 per cent by volume. These deviations were believed to depend on different factors, such as the age of the lesion, structure and chemical composition of the enamel, properties of plaques, saliva and ingested carbohydrates, or trace elements such as fluorine. In two cases, where superficial cavitation had occurred, the mineral curves exhibited an irregular course. The maximum decalcification in these cases, however, did not exhibit significant deviations from corresponding values in the nine cases with unbroken surface zone. No hypercalcified zones were found within or in the vicinity of the carious lesions. Micro-X-ray-diffraction analysis of two cases within an area with advanced decalcification revealed well-oriented hydroxyapatite in the carious enamel.

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