EFFECTS ON THE TEETH 157 



chemical composition of the teeth is also changed, with an increase in water 

 content and a decrease in nitrogen and ash. 



Talbot ('09) and others have pointed out the importance of malnutrition 

 in connection with defective teeth of children. Sill ('09), for example, in 1,000 

 school children 6-12 years of age in the Jewish quarters of East Side, New 

 York City, found 40 per cent malnourished, more or less anemic and under 

 weight; while 86 per cent had dental caries. He believes that dental caries is a 

 causative factor in malnutrition. It might, however, be an effect, rather than a 

 cause; or possibly a "vicious circle," malnutrition producing defective teeth, 

 which in turn tend to prevent an adequate food-intake. Emerson ('22), how- 

 ever, found no increase in caries among malnourished children. 



Tschkwinsky ('10) observed that in underfed lambs there is a delay in the 

 replacement of the temporary with the permanent incisors. Jackson ('15a) 

 found that in albino rats held at constant body weight by underfeeding from 

 3-10 weeks of age, there is a progressive development of the teeth, the formation 

 and eruption of the third molars proceeding in spite of the stationary body 

 weight. This was confirmed by Stewart ('18). Similarly Boas ('23) finds that 

 among poor children the eruption of the permanent teeth is not retarded, as is 

 the general body development. It therefore appears that the teeth share with 

 the skeleton the persistent tendency to growth during incomplete total inanition 

 (general underfeeding). 



Bean '(14) and others have suggested the relative development of the teeth 

 (appearance and replacement of the deciduous teeth) as a method of determining 

 the "physiological age" of children. This would appear to be a more conven- 

 ient index than the height or skeletal epiphyses, but infortunately there has not 

 been as yet a sufficient investigation of the correlation of dentition with skeletal 

 and other changes during retardation of growth in malnourished children. This 

 is necessary before it can be determined how reliable is the stage of dentition 

 as an index of "physiological " (or better "anatomical") age, in comparison 

 with "chronological" age. 



(B) Effects of Partial Inanition 



King ('18) incidentally noted the frequent occurrence of defective teeth in 

 rats suffering from malnutrition on diets which apparently contained relatively 

 too much starch and too little protein. 



Mineral Deficiency. — Aside from observations in connection with rickets, 

 not much is known as to the effects of dietary mineral deficiencies upon the 

 structure of the teeth. Miller ('87) found a very slight apparent decrease in 

 calcium content in the teeth of adult dogs after 13 weeks on a calcium-poor 

 diet. The deficit is restored by refeeding on a diet rich in calcium. Leonard 

 ('20) observed imperfect formation of enamel in many infants 6 months to 3 

 years of age. This was ascribed to malnutrition from diets lacking in essential 

 salts and vitamins, but did not appear in the permanent teeth of the older children. 



Rachitis. — Irregularity of the teeth in rickets was noted even by Whistler 

 (1645) and Glisson (1650). An abnormal delay in the eruption of the teeth in 



