The number of persons with markedly worn teeth does not appear to be directly related to the fluoride content of the water consumed. There is a suggestion, however, that the wearing down process starts earlier in places with exceptionally high levels of fluoride in the water. The teeth most commonly affected were the central incisors. In some advanced cases, more than half of the total of the normally exposed portion of the tooth had been worn away. There did not seem to be any great prevalence of teeth that had crumbled or broken. This was judged from the rather subjective observation that a broken tooth would leave an irregular rough area at the site of fracture, whereas a worn tooth has a smooth surface.

2. Dental Caries-The prevalence of dental caries was found to be very low (Table 3). Of the 1,243 persons examined 76.8 per cent had no teeth that were decayed, missing, or filled other than those that had been extracted for tribal reasons. During the examination, the authors formed the opinion that periodontal disease was common and many teeth which have been recorded as missing, especially in older persons, may have been lost as a result of this cause rather than because of caries.

The total number of teeth decayed, missing, or filled (DMF) was 719, giving a DMF index of 0.58.

3. Nail Changes-The nail changes were diverse in character. The commonest findings were longitudinal striations often quite deep. Other abnormalities included those of contour such as spoon shaping, converse watch glass curvature, or flattening, changes of color, such as
brownish pigmentation or abnormal speckling, and alteration in surface texture, such as pitting and roughening.

Table 4 shows that nail abnormalities were common among all the different groups examined. Of the 1,243 subjects in the survey, 43.8 per cent were found to have nail changes. There does not seem to be any significant relationship between the prevalence of nail changes and the fluoride content of the water in the various areas.

While examining the nails it was noted that 18 persons had marked clubbing of the fingers of both hands. They were all adults and 15 were over 40 years of age. No pulmonary or cardiac cause for the clubbing was evident in these subjects and none had cyanosis.

4. Goiter-Table 5 shows that goiter was a common finding in the persons examined in this survey. In all, 27.4 per cent of subjects had thyroid glands recorded as being more than five times their normal size. Only 16 (4.7 per cent) of the goiters were adenomatous (nodular). There appears to be no significant link between goiter prevalence and fluoride content of water in the different areas.

. . .

The survey has revealed a goiter rate of 27.4 per cent. Galletti and Joyet and others have suggested that fluoride inhibits the thyroid iodide concentrating mechanism and that when the total iodide pool is low may impose a critical
limitation on hormonal synthesis. Studies in South Africa have incriminated excess fluoride intake as a leading cause of goiter in several endemic areas there. The prevalence of goiter in subjects in the present survey is higher than the 13.8 per cent found in the Rufiji District12 or the 9.7 per cent found in the Central Region of Tanzania. However. it is considerably lower than in the goiter endemic Ukinga highlands where goiter was found in 75.9 per cent, the highest goiter rate so far recorded in Africa. In none of these areas has fluorosis been found. It is, therefore, not at present clear whether fluorine is a factor in the goiter found in the Arusha district.