The most important condition in the etiology of caries is the oral environment of the teeth—the purely external factors that act on their surfaces. Diet, in its relation to dental oral-environment, is the principal factor. Detergent and cleansing actions of the diet of primitive groups are very important in defence against caries. High incidence of caries in civilized races appears to be due to a combination of factors intimately connected with refinements of modern ” civilized ” diets. Primitive Bantu of South Africa are relatively immune to caries. This degree of immunity (a) is greatly diminished when habits and modes of life associated with civilized surroundings are adopted (although urban Bantu are less susceptible to caries than the European races of South Africa) ; (b) is not due to any inherent differences in teeth; and (c) appears to be dependent upon a combination of factors external to teeth. The slight susceptibility of primitive Bantu to caries may be due to fermentation of carbohydrates in the sugar cane and honey in their diet. Compared with the amounts of sugar consumed by Europeans and urban Bantu, the quantities eaten by primitive Bantu are relatively small. In this fact is probably found the chief explanation of the relative immunity of the Bantu to caries.
In composition, microscopic structure, and reaction to acids, the teeth of primitive Bantu do not differ in any way from European. No hypoplasia has been found in teeth of Bantu, although in the primitive state they often live on diet deficient in essential food factors ; their intake of calcium and phosphorus is usually low ; and, although largely vegetarian, they receive a bare sufficiency of vitamins, either in food or through exposure to sunlight—several have shown deficiency of vitamin C; yet there is high resistance to caries. One of the most important factors rendering primitive Bantu relatively immune to caries is the shape of the jaws. When Bantu adopt diets associated with civilization—even when there is either no decrease in the quantity of vitamins or an increase—the jaws and teeth deteriorate. In primitive Bantu the mouth environment appears to be neutral or slightly acid ; in the European mouth, there is greater acid concentration; urban Bantu are intermediate. These conditions agree with the fact that caries occurs in greatest degree in Europeans—least in primitive Bantu. Compared with Bantu, Europeans show more carious cavities, and greater oral acidity. The mechanical factors in the superior masticatory apparatus of Bantu, or the cleansing effects of primitive foods, increase resistance of Bantu against caries. Ropey saliva and ” dirty mouth ” are often associated with the greatest degree of caries in primitive Bantu ; but not in Europeans of South Africa. The main article of Bantu diet is maize. This cereal, when prepared in primitive fashion, has no apparent deleterious effect on development, structure, composition or subsequent behavior of teeth. The action of sour milk in primitive diets, as opposed to fresh sweet milk in civilized diets, appears to be an important factor in prevention of caries. The Bantu exhibit marked susceptibility to degeneration of gums and adjacent tissues. Factors that frequently cause unhealthy conditions in Europeans are often absent in Bantu, yet the latter race appears to be highly susceptible to degeneration of the soft tissues of the mouth.
Reference: S. Afr. J. Med. Sci. (suppl.), 1938.