KNUTSON, J. W.: National Institute of Health, Office of Child Hygiene, Washington, D. C. (Oct. 10, 1938).

 [For himself and co-workers, CAR-ROLL E. PALMER and HENRY KLEIN.]

Tooth mortality in elementary school children. Loss of permanent teeth in elementary school children is largely a problem of loss of first molars, these accounting for at least 90 percent of the total tooth-mortality for each age- and sex-group of 4416 children, ages 6 through 15. Of the total deaths of permanent teeth, the lower first molars contribute 70 percent in boys, and approximately 80 percent in girls. In large groups of children, tooth mortality is bilaterally equal for each morphological type of tooth. Boys having caries, without objective evidence of dental fillings, have 58 percent more missing permanent teeth, 60 percent more missing first permanent molars, and 61 percent more missing lower right first permanent molars, than boys having caries, with approximately one-half of their carious permanent-tooth surfaces filled. The marked similarity in these respective comparative values sug­gests that annual mortality rates of the lower right first permanent molar, specific for age and sex, should afford data for a relatively accurate evaluation of dental care in elementary school children.

Relative incidence of caries in different permanent teeth. Analysis of the dis­tribution of caries in the morphological types of permanent teeth per 100 children

—for specific age- and sex-groups in 4416 elementary-grade school children, ages

6 through 15—indicates that girls have a higher incidence of caries experience in each type of tooth for each chronological age than boys. Arranged in the order (decreasing) in, which specified kinds of permanent teeth contribute to the total caries experience, specific for age and sex, lower first molars and upper first molars consistently maintain first and second positions, respectively. The relative posi­tions of the other teeth change fairly rapidly with advancing chronological age. This change is characterized by marked tendency for lower second and upper sec­ond molars to rise to third and fourth positions, respectively, while lower incisors, lower canine, lower first bicuspid, and upper canine—all of which are characterized by low caries-attack rates—move downward to the last five positions. Ages 13 to 15 represent that chronological age-span (both sexes) when number of carious teeth in each jaw is about equal ; up to age 13 more lower than upper teeth are carious ; but the decided trends in age distribution of caries in the jaw segments indicate that, after age 15, more upper teeth than lower are carious. Wide differences in the chronological age at which the types of teeth erupt make it necessary to use the mean age of eruption as a base line (instead of chronological age) to determine relative susceptibility of different teeth to caries. The results of such a procedure indicate that (a) lower second molars have the sante order of susceptibility to caries as lower first molars ; (b) upper second molars have about the same order as upper first molars ; (c) in general, the molars have the highest order ; the upper incisors, upper first and second bicuspids, and lower second bicuspids have an in­termediate order ; the lower incisors, lower canines, lower first bicuspids, and upper canines have the lowest order.

References: Pub. Health Rep., 53, 1938; J. Am. Den. Assoc., 25, 1923, 1938.

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