In caries the surface lesion is produced by coccoid bacteria. The causative mechanism is internal. Factors that account for predisposition to caries include absorption and retention of mineral salts, endocrine balance, histologic structure of dental tissues, and heredity.
Organic matrix of decalcified human enamel includes all histologic structures ever described in ground sections, and more. The following structures are seen after complete solution of calcific matter : (a) enamel rods, (b) cement substance, (c) alternate bands, (d) striae of Retzius, (e) enamel spindles, (f) lamellae, (g) Nasmyth’s membrane. In caries there is ” condensation ” of the organic content of rods, which are attacked first ; cement substance is more resistant. Brownish discoloration of enamel seems to be due to keratinization ‘ of organic matrix, making it very resistant to lytic action of acids and alkalies. In impacted and retained teeth, enamel may undergo resorption that is microscopically identical with that of bone, dentin, and cementum. Experimental studies have confirmed this observation, and have also shown that pathological conditions of the soft and hard tissues of teeth and jaws occur in disturbances of calcium-phosphorus metabolism.
References: J. Den. Res. (with S. N. Blackberg), 1932, 1937; Den. Cosmos, 1936.