KLEIN, HENRY, and PALMER, CARROLL E.: Division of Public Health Meth­ods, National Institute of Health, U. S. Public Health Service, Bethesda, Md. (May 12, 1939).

(1) Study of the kinematics of carious attack requires development of basic epidemiological constants. In this connection the finding that age dis­tribution of tooth eruption may be described accurately by the normal proba­bility function makes possible the construction of standard tables giving the tooth-years-of-exposure-to-risk of carious attack of each kind of tooth in the permanent dentition. (2) Specific caries-susceptibilities of individual teeth and surfaces may be defined on the basis of post-eruptive tooth-age. The teeth in decreasing (highest to lowest) order of susceptibility are lower first and second molars, upper first and second molars, upper central incisors, upper lateral incisors, upper first and second bicuspids, lower second bicuspid, lower first bicuspid, lower central and lateral incisors, and all canines. (3) Since the end result of neglected caries is loss of teeth, counts of ” odontothanatosis ” (number of non-vital and extracted permanent teeth) per 100 children pro­vide a means of estimating the level of dental care in a population group.

(4)            Familial resemblances in dental caries are indicated by the finding that brothers and sisters of relatively immune cases show one-half as much caries as do brothers and sisters of children who are relatively caries-susceptible.

(5)            Sex differences in caries (girls have more caries than boys of the same chronological age) are explained quantitatively by the finding that girls, be­cause their teeth erupt earlier than those of boys, are exposed longer (have a greater post-eruptive tooth-age) than boys to the risk of attack by caries. (6) Dental needs in children represent accumulations of neglected yearly in­crements of caries attack. New carious defects accrue in permanent teeth of grade-school children at a rate (1.3 carious surfaces per child per year) approximately six times greater than that at which surfaces are being filled (0.23 surface filled per child per year). (7) Caries-prevalence [percentage of children having one or more carious, missing, or filled (DMF) permanent teeth] increases with age at different rates for different American Indian tribes and tribal aggregates, the rates being lowest for the southwestern areas —highest for the northwestern—in the United States. (8) Pregnancy per se does not appear to increase susceptibility to caries. Lactation may be so related, but has not yet been demonstrated. (9) Carious lesions in rat molars grossly simulate those in human teeth. The defect occurs in pits, on the cusps, and interproximately in enamel of embrasure. Rats on stock diets with grains develop microscopic carious lesions. Vitamin-D feedings appear to reduce, and suboptimal diets tend to increase, incidence of these defects.

References: J. Den. Res., 1932; Am. J. Physiol., 1935; Den. Cosmos, 1935; Pub. Health Bull. No. 239, 1937; Pub. Health Rep., 1938; Growth, 1938; Child Development, 1938.

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