LACTOBACILLUS TEST IN CONTROL OF DENTAL CARIES 8• Lactobacillus counts are not reduced following the topical application of fluoride. This may be due to the fact that the solution lowers the solubility of the tooth surface so that lesions may not necessarily occur under bacterial plaques which contain acid producing organisms. On the other hand, it may simply mean that the reduction in caries activity is not great enough to be measured by differences in bacterial coun rs. Zander (4) has recently reported the reduction of caries in school children who used a tooth powder containing penicillin. Although the results were not published, Lacto- bacillus counts were run on these children. Apparently ' (5) there was a drop in the Lactobacillus counts at the onset of the study, but at the end of the entire period of observation the Lactobacillus counts were not significantly different in the experimental and control groups. It would seem from this that the Lactobacilli did not serve as an index of caries activity. The possibility, however, must not be overlooked that should the Lactobacillus cou•nts remain at the original level, caries activity may eventually return to its previous intensity. This can only be determined by future ob- servations. It is perfectly safe to use the Lactobacillus test as a measure of the effectiveness of dental caries control diets. Whether or not this method will serve equally as well as a test of the efficacy of drugs will require further study. REFERENCES (1) Hadley, F. P., "A Quantitative Method for Estimating Bacillus Acidophilus in Saliva," 5 e. Dent. Res., 13, 415 (1933). (2) Jay, P., "Fluorine and Dental Caries with Special Reference to L. Acidophilus." In Moulton, F. R., ed.: "Fluorine and and Dental Health," Pub. No. 19, Am. Assoc. Advancement Sci., Lancaster, Science Press (1942). (3) Becks, H., Jensen, A. L., and Millart, C. B., "Rampant Dental Caries: Pre- vention and Prognosis," )t. Am. Dental Assoc. ,31, 1189 (1944). (4) Zander, H. A., "Effect of a Penicillin Dentifrice on Caries Incidence in School Children," 5 •. Am. DentalAssoc., 40,569- 574 (1950). (5) Personal communication.

THE SYRIAN HAMSTER AS A TEST ANIMAL FOR THERAPEUTIC DENTIFRICE STUDIES* By J. F. VOLKER, University of •llabama, School of Dentistry, Birmingham 5,/lla. THE BEST AVAILABLE IN- FOR•4ATIO• indicates that dental caries is an endem. ic disease afflicting over 98% of the American popula- tion. The severity of the disease, however, is not often appreciated. It can be best understood by a con- sideration of the data accumulated in representative studies (1, 2) on children from age 7 to adults through the age of 34. These show that the average seven-year old American has evidence of decay in 1.4 of his permanent teeth and that this increases by slightly less than one permanent tooth per year until 18 years of age, at which time on an average of 11.2 teeth have been affected. From this age the yearly increment of new carious teeth is at the rate of approximately one- half a carious tooth per year. As a result, persons in the 30- to 34- year-old-age group have on an average 20.2 carious teeth. From these findings we can make a gen- eralization that the average Ameri- * Presented at the May 19, 1950, Meeting, New York City. can will experience tooth decay in his permanent dentition within two years after his permanent teeth have begun to erupt and that he will have carious experience in over 50% of his permanent teeth at age 30. This is shown graphically in Figure 1. 2O 8 10 12 14 Iõ Iõ 20 22 24 26 28 30 32 34 AGE IN YEARS Figure 1.--Incidence of Dental Caries It is of major importance that therapeutic agents capable of limit- ing tooth decay be developed. Lately, the possibility that sub- stances possessing these properties may be incorporated in dentifrices has received considerable attention. Unfortunately, many materials which in in vitro tests have given