MID-MORNIXG LUNCH IN RURAL SCHOOLS 43 



Influence of Feeding on Dental Caries 



On first thought it might seem an easy matter to compare the incidence of 

 caries during a period of time in two groups of children. It did not prove to be so 

 simple, however, because of the changing number of teeth as the temporary 

 ones are lost and the permanent are erupted; and because of the variation in the 

 susceptibility to caries of different mouths and of different teeth in the same 

 mouth. 



By June most of the first-grade children had acquired their si.\-year molars 



and had begun to lose their temporary teeth: b>- ten years of age, the latter had 



all disappeared in the majorit\- of cases, and the child had 24 permanent teeth 



unless he had been so unfortunate as to have had some extracted; and by twelve 



years, the second molars had begun to appear in many cases. The picture thus 



varied with the age of the children; and if temporary and permanent teeth were 



to be considered separately, it was necessary to make the comparison at each 



age. It was noted, however, that from six to twelve years inclusive there was 



but little variation in the total number of teeth per child, and also that the mean 



number of carious teeth was approximately the same irrespective of age. This 



y% ^nalysis, therefore, has been made on the basis of the total number of teeth 



A .leather than on the basis of temporar\- and permanent teeth separately for children 



' Nf '* from five to twehe >ears of age. 



Because of the loss of the temporary teeth, it was obvious that the difference 

 between the number of caries found at the first and second examinations was not 

 always an indication of the number which had developed in the interval between 

 the two. To illustrate: B3L5 was found to have 9 carious teeth in September. 

 In June he had but 8; but while he had lost 3 carious temporary teeth, new 

 caries had developed in 2 other teeth. As a result his teeth were reall>' in as 

 poor condition in June as in September. A more logical approach, therefore, 

 seemed to be to observe the number of teeth found at the June examination in 

 which caries or pits and fissiires had developed since the preceding fall, and to 

 note whether an>- fewer had appeared in the fed than in the control children during 

 the period of feeding. 



That indiv'idual mouths vary in susceptibilit\- to caries is a well-known fact, 

 and whatever the cause, the disease seems to be more rampant in some groups 

 than in others. It is also to be expected that fewer new caries will develop during 

 the year in mouths which had the fewest at the beginning. A larger proportion 

 of sound teeth was found among the Italian children of school C than among 

 the other children. Accordingly the condition of each child's teeth was rated 

 on the basis of the number of carious teeth found at the fall examination, as follows: 

 Percentage 



of Teeth Rating 



Carious 



0— 9 E.xcellent (E) 



10— 29 Good (G) 



30— 49 Fair (F) 



50— 69 Poor (P) 



70—100 Very Poor (\'P) 



The results of this anaKsis are given in Table 1.5. As was to be expected, 

 the mean percentage of teeth in which new caries and new pits and fissures had 

 appeared during the experimental period was lowest for those whose teeth were 

 excellent at the beginning of the stud\'. Between the experimental groups there 



