210 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946: 
spread rapidly, and it began to appear in water analyses. Because 
the early emphasis was entirely on the problem of mottled enamel, 
small amounts of fluorine were at first considered of no significance. 
A few of the answers to our inquiries stated that no tests for fluorine 
had been made because the area had no problem of mottled enamel. 
The areas covered by the “general statements” are areas of low fluorine 
content, and a general statement to that effect was considered sufficient, 
whereas when the fluorine content was high, the exact amounts were 
almost always given. 
It should be pointed out here that partly because of this thought pat- 
tern, emphasizing the importance of large amounts of fluorine, and 
partly because the early methods of analysis were not sufficiently re- 
fined, the early analyses showing small amounts of fluorine must be 
used with caution. They may sometimes err by as much as 0.4 or 0.5 
D..p:,m.? 
This emphasis on the problem of mottled enamel is understandable 
for several reasons. Mottled enamel is a positive disfigurement, a 
definite abnormality endemic in certain specific regions. Dental 
caries, on the other hand, is usually much less obvious in its effects on 
personal appearance and is so much more widespread that it is almost 
taken for granted as a normal condition. Mottled enamel is attribu- 
table solely to excesses of fluorine, a relationship which was discovered 
in 1931. Dental caries can be attributed only in part to deficiencies of 
fluorine. It was first actually demonstrated in 1937 and 1938, by 
studies of the chemical composition of sound and carious teeth and 
by epidemiological studies of children in cities using water of different 
fluorine concentrations.” 
In the number of people affected, there is no doubt that dental caries 
is a much vaster problem than mottled enamel. It is to be hoped, 
therefore, that there will be a more general recognition of the im- 
portance of knowing the exact amount of fluorine in our water sup- 
plies, whether it is much or little. It is only fair, however, to point 
out that such recognition is already more widespread than might 
appear from the map. In a number of areas where no fluorine tests 
have yet been made the reason has not been failure to realize the need 
but a lack of trained workers and equipment brought about by the 
war. 
® Personal communication from Dr. H. Trendley Dean. 
10 Armstrong, W. D., Fluorine content of enamel and dentine of sound and carious teeth, 
Journ. Biol. Chem., vol. 119, proce. 5, 1937; Armstrong, W. D., and Brekhus, P. J., Possible 
relationship between the fluorine content of enamel and resistance to dental caries, Journ. 
Dental Res., vol. 17, pp. 393-399, 1938; Dean, H. Trendley, Endemic fluorosis and its rela- 
tion to dental caries, Publ. Health Reps., U. S. Public Health Service, vol. 53, pp. 1443- 
1452, 1938; Dean, H. Trendley, Jay, Philip, et al., Domestic water and dental caries, includ- 
ing certain epidemiological aspects of oral Lactobacillus acidophilus, ibid., vol. 54, pp. 862- 
888, 1939. 
