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Osborne-Mendel rats 22–25 days of age were subjected to a 7-day precaries test period during which they were fed a high starch diet and drank distilled water containing no added fluoride or with 10, 50, 100 or 150 ppm fluoride as sodium fluoride. After this period, 36 animals from each group were provided with distilled water during a 56-day caries test period (fed diet 2000 and infected with Streptococcus mutans 6715). Fluoride content in the enamel was shown to be directly related to the level of fluoride in the drinking water during the initial 7-day exposure period, both at the end of this 7-day period of fluoride treatment and at the end of the caries test period. Caries development was inversely related to fluoride uptake in the enamel; animals which received 50 ppm or more fluoride developed significantly fewer carious areas than the controls. 36 additional animals from each pretest group were subjected to the same caries test challenge as above but in addition were provided with 10 ppm fluoride in the drinking water. Caries development in these groups was extremely low even though there was no increase in the fluoride content of enamel in animals drinking water containing 10 ppm fluoride during the caries test period. Fluoride provided prior to the caries test regimen conferred the most protection on the sulci, in contrast, fluoride provided during the caries test regimen had a more pronounced effect on the smooth surfaces and in addition had a greater overall effect.

This study was conducted to determine whether glucose tolerance curves for parotid salivas of diabetics were different from those for non-diabetics. Since Langley, Gunthorpe, and Beall (Amer. J. Physiol., 192:482-84, 1958) have shown that the glucose threshold for parotid secretion varied directly with insulin dosage in dogs, it was thought that lack of insulin in man might so lower the parotid glucose threshold that large quantities of glucose would appear in saliva. If so, analysis of parotid fluid might be as useful as analysis of blood or urine in the diagnosis of diabetes mellitus.Early-morning samples of venous blood and parotid saliva were collected from 26 uncontrolled diabetic and 26 non-diabetic persons, aged twelve to seventy years, in the postabsorptive state just prior to, and at about 30, 60, 120, and 180 minutes after oral administration of 1 gm. * Mean and standard deviation. per kg. of body weight. At each collection time, venous blood was drawn, and approximately 5 ml. of parotid saliva stimulated with lemon juice was obtained by means of a parotid cap. Collection of saliva was completed about 7 minutes after each blood sample was drawn.Glucose concentrations were determined by the method of Saifer and Gerstenfeld (J. Lab. clin. Med., 51:448-60, 1958) on duplicate samples of 0.2 ml. of deproteinized plasma and 2 ml. of non-deproteinized parotid saliva.Glucose concentrations in parotid secretion varied directly with plasma concentrations for each subject but at a much lower order of magnitude (see the accompanying tabulation).Although average glucose concentrations in parotid saliva for diabetic subjects were slightly higher at each time period than those for non-diabetic subjects, there was considerable overlapping of curves for individuals in both groups. Therefore, it is doubtful that parotid glucose concentrations could be useful, or replace the use of plasma, in the diagnosis of diabetes mellitus.