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volume 79, no. 3 177 Reprinted from Connecticut Medicine, March, 1965; 29(3):161- 162, 165, 172. Mutual Medical Dental Problems: Fluoridation of Water Supply LOUIS H. NAHUM, MD C onnecticut has prepared legislation that fluorida- tion be mandatory for water supplies serving ten thousand or more persons. is measure is at present on its way through various state public health and legislative channels. If the law should pass, the engineering phases of fluoridation are well enough understood to permit easy application within approved safety limits for accuracy. e costs continue to be reported at between five and fifteen cents per person per year and these costs are far below those of any other type of fluoride program. ere are acceptable though scantily tested alterna- tives to water fluoridation at considerably increased cost and reduced practicality. ese measures include programs using fluoride tablets and solutions, addi- tion of fluoride to foods and topical treatment of teeth with concentrated fluoride solutions. Aside from the increased cost, it is obvious that such measures will reach but a small proportion of our population. There are now forty-six million persons in this country drinking fluoridated water and another seven million living in communities with natural fluorides of optimum or greater concentration in their drinking water and in 1965 an additional eight and one-half mil- lion will be added when New York City fluoridates its water supply. So that we are now in a position to study the effect of water fluoridation on dental caries by com- paring populations that drink fluoridated water with those that don't. Of those that don't drink fluoridated water, ninety-nine per cent of the population gives some evidence of dental caries upon reaching adulthood. e average child in Massachusetts at age fourteen has already lost one tooth from dental caries and has four teeth filled and seven others in need of filling. 1 In short, half of the permanent dentition of these children has been damaged and less than half that needed dental restorative treatment have had it performed. Aside from fluoride therapy, the common preventive measures for dental caries include tooth brushing and diet. Nevertheless, there is little evidence that they have resulted in important reduction in caries under test conditions and there is considerable evidence that over the years these measures have failed to prevent an increase in dental caries experience in large population groups. Somewhat better evidence exists for the benefi- cial effect of restriction of carbohydrate in the diet, but again large population groups have failed to make use of this measure and may be expected not to in the future. In the meanwhile, fluoridation has produced massive evidence of large reductions in dental caries in large populations. We may define fluoridation as the adjust- ment of a water supply to a fluoride content at which a reduction of fifty to seventy per cent in dental caries will occur without damage to teeth and other structures. In this climate the optimum content is one part per million (1 mg. per liter .2 Newburgh, New York, after fifteen years of fluoridation shows a reduction of seventy per cent in dental caries experience as compared to Kington, New York, among children thirteen to fourteen years of age, and a reduction of ninety per cent in numbers of missing teeth per child. ere are many similar studies in all communities where fluoridation was in effect, so that there is no longer any reason to doubt the fact that adjustments of a community water supply to optimum fluoride concentration greatly reduces dental caries, an observation long known to occur in populations that drink naturally fluoridated water. e mechanism by which fluoride acts is considered to be chiefly a replacement of hydroxyapatite by the less soluble fluorapatite in the crystalline structure of tooth enamel. 3,4 Possible additional mechanisms are indicated by the fact that fluorine favors the prepita- tion of calcium phosphate from saturated solutions and that it inhibits some and stimulates other enzyme action. Catalytic action upon enamel crystallization may also be involved. ere is also a higher concentra- tion of fluoride in bacterial placques close to the tooth surface which permits local reactions not typical of the concentration of fluoride in saliva or other body fluids, thereby reinforcing the fluoride in the tooth enamel. When fluoridated water is ingested there is rapid absorption of over ninety per cent of soluble fluoride, of which half appears in the urine and the rest is stored in bone and teeth. No fluoride is stored in soft tissues. e urine excretion is prompt and responds in sensitive fash- ion to low doses. As age advances gradual accumulation DR. LOUIS H. NAHUM, Lecturer in Physiology, Yale University School of Medicine, New Haven. Consultant in Medicine, Hospital of St. Raphael, New Haven. Griffin Hospital, Derby. Middlesex Hospital, Middletown. Cardiologist, Milford Hospital, Milford.