JEANNERET, RUDOLF : University of Berne, Berne, Switzerland (Sep. 10, 1938).

Miller’s theory on the course of the carious process has been confirmed, but the basic cause of loss of resistance to caries points to problems of domesti­cation and diet. Correlations of data for chemical composition of enamel and of diet have not explained etiology of caries. There has been unwar­ranted tendency to ascribe to rickets, scurvy, and other avitaminoses direct causal relations to caries. The role of hypovitaminotic conditions cannot be overestimated, especially since their latent stages—not easily recognized—act during long periods on developing teeth (before and after eruption), but close investigation of diets of primitive peoples having high resistance to caries indicates difficulties in showing direct correlation with certain food factors. In comparison with results of laboratory experiments, many con­tradictions are encountered. The consistency of food is related to the ex­ternal exciting causes of caries. Mastication of hard detergent food has the same relative protective influence as tooth-brushing, both of which are unneces­sary under conditions of high resistance to caries.

In two districts, in which there were marked differences in ” hardness ” (cal­cium and other mineral contents) of the drinking water, but in which living condi­tions of both populations were about the same, the teeth of the children in the district having the ” hardest ” water showed more caries than those in the other district. The theory of Roese and others, that increased incidence of caries is directly correlated with a low proportion of calcium in the drinking water, was not confirmed. Errors in the statistics of Roese and other investigators in this field were demonstrated. Different breads had the same relation to the pH of dental plaques, irrespective of their nutritive value. A variety of breads showed primary acidity (pH 4.6 — pH 6.3). At body temperature, all slowly produced secondary acidity which in 24 hours amounted to pH 4.2. When saliva was added, the total acidity amounted to pH 4.7-4.4 in three hours (average 4.6) with all kinds of bread —rye or wheat, baked by different procedures, fresh or stale.

References: Schw. Monat. Zahnh., 1929, 1936, 1937, 1938 ; Z. Vitaminforsch., 1937—(with H. L. Lauener) 1930, (with J. A. Breitenmoser) 1931.

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