Attempts to alter the calcium content of dentin have been ineffective; it is even more unlikely that enamel could be altered. Tissue fluid cannot reach the carious lesion, and clinical attempts to treat caries by nutritional methods have been useless. Caries can, however, be held up indefinitely by local chemical treatment (e.g., silver nitrate in children), mechanically (by attrition in savages), or bactericidally (in dogs). Caries is a bacterial decomposition of tooth substance, which can be affected only by local conditions such as food stagnation and fermentation, or immunologically through saliva.
Immunity of savage races to caries varies in direct ratio with the degree of attrition. Totally immune primitive skulls show not only the fissures entirely ground away, but also interproximal wear with facets half through the enamel. The dog’s immunity to caries appears to be due to an anti-bacterial principle. A human carious tooth fixed in a dog’s mouth becomes sterile in from two to four days. In a susceptible monkey’s mouth, the organisms do not die out and S. mutans can be recovered from an implanted human tooth after eleven days. The calcium content of dentin cannot be altered, once it is formed, by (a) administration of vitamin D or by (b) calcium starvation in pregnancy. As soon as dentin is contaminated by toxic products of a carious lesion in enamel, that area of dentin is at once cut off from the pulp by an impermeable barrier of calcified matrix. Tissue fluid cannot, therefore, reach the lesion to help in any way in arresting the progress of the disease.
References: Den. Cosmos (with Ian Maclean), 1934; J. Physiol., 1935; Experimental investigation of enamel, dentin, and dental pulp, 1932 (John Bale, Sons and Danielsson, London).