The Conclusion of a Ten-Year Study of Water Fluoridation DAVID B

Official Monthly Publication of the American Public Health Association, Inc.

Volume 46 March, 1956 Number 3

The Conclusion of a Ten-Year Study of Water Fluoridation DAVID B. AST, D.D.S., M.P.H., F.A.P.H.A., and EDWARD R. SCHLESINGER, M.D., M.P.H., F.A.P.H.A.

extent as observed in areas where water Here in capsule form is a resume of the Newburgh-Kingston Caries- contains the fluoride at the source. A Fluorine Study after a decade, with recent review 3 presented the DMF (de- some additional information on the cayed, missing, or filled teeth) rates for safety of water fluoridation. six- to 10-year-old children after nine years of fluoride experience in Grand Rapids, Mich., Newburgh, N. Y., and In areas where the potable water supplies contain the fluoride ion at Brantford, Ontario, and compared these data with those in Aurora, Ill., which optimum concentration at the source, the dental caries experience of children uses a water supply with naturally oc- who ingest these water fluorides during curring fluoride at 1.2 ppm F. At ages six to nine the rates in all four com- the years of tooth development is about munities were found to com- 60 per cent less than among children be quite parable and at age rates in areas with fluoride-deficient water 10 the for the supplies.' Adults who have used such three communities fluoridating their water supplies continuously enjoy the water supplies approached the expect- dental benefits obtained during child- ancy level noted in Aurora. hood.2 One of the most comprehensive of Controlled water fluoridation for the the studies, the Newburgh-Kingston prevention of dental caries, i.e., the ad- Caries-Fluorine Study has recently is- dition of fluoride compounds in optimum sued its final report based on 10 years concentration to fluoride-deficient sup- of fluoridation experience. The report, plies, has been studied since 1945 in consisting of three definitive papers three different areas. These studies have demonstrated that dental caries Dr. Ast is director, Bureau of Dental Health, and Dr. Schlesinger is associate director, Di- can be effectively reduced through con- vision of Medical Services, New York State trolled water fluoridation to the same Department of Health, Albany, N. Y. 265 266 MARCH 1956 AMERICAN JOURNAL OF PUBLIC HEALTH

dealing with the history of the study mend the types of medical and dental and its pediatric and dental aspects, and examinations which should be made to a fourth paper dealing with fluoride determine the efficacy and safety of metabolism, was presented before the water fluoridation. After a careful re- New York Institute of Clinical Oral view of the literature and the objec- Pathology on December 12, 1955. These tives of the study, the committee recom- papers appear in the March, 1956, issue mended that a long-range study be un- of the Journal of the American Dental dertaken. The cities of Newburgh and Association.4-7 Kingston, each with a population of Prior to the initiation of controlled approximately 30,000, situated about 35 water fluoridation programs in 1945 miles apart on the west bank of the extensive epidemiological investiga- Hudson River and using fluoride-de- tions 8a, b had demonstrated (1) the oc- ficient water supplies, were asked to currence of a defect of tooth enamel participate in a 10-year study. New- which discolored and, in extreme cases, burgh agreed to serve as the study area caused pitting of the enamel; (2) the and to have its water supply supple- discovery that the stain or mottled mented with sodium fluoride to bring enamel was caused by the ingestion of its fluoride content up to 1.0-1.2 ppm. water-borne fluorides during the years Kingston agreed to serve as the control of enamel calcification; (3) the direct and continue to use its water supply relationship of the degree of mottling with approximately 0.1 ppm F. to the fluoride content of the water; In June, 1944, base line pediatric and (4) an inverse relationship of dental dental examinations were begun and caries to fluorosed or mottled teeth; and on May 2, 1945, Newburgh's water sup- (5) that where the water supply con- ply was flioridated. This process has tained approximately 1.0 ppm F, the been in continuous operation since that residents enjoyed considerable protec- date. The base line data showed that tion against dental caries without the the children aged six to 12 in both cities hazard of disfiguring mottled enamel. had a similar dental caries experience. Cox and his co-workers 9 in 1939 The Kingston rate was 20.2 DMF teeth suggested that the addition of flfuorides per 100 permanent teeth and the New- to food and water to bring the fluoride burgh rate was 20.6. Periodic progress content up to the optimum level could reports have demonstrated a downward prevent dental caries if ingested during trend in the dental caries experience the years of tooth development. Ast 10 among the children in Newburgh. In in 1942 outlined a plan to test the caries- Kingston the caries rates have remained fluorine hypothesis. He suggested a relatively unchanged. study of two comparable communities In June, 1955, clinical and intraoral with fluoride-deficient water supplies, dental roentgenographic examinations one of which should have its water were completed after 10 years of fluoride supply supplemented with sodium experience. In Newburgh 1,519 chil- fluoride to bring its fluoride content up dren aged six to 14 and 109 aged 16 to 1.0 ppm and the second to serve as who had had continuous residence there a control. throughout the period of fluoridation This plan was considered by the New were examined. The Kingston children York State Department of Health. In examined included 2,021 aged six to 1944 a Technical Advisory Committee 14 and 119 aged 16. The clinical ex- on the Fluoridation of Water Supplies aminations were made in both cities by was appointed to study the proposal. the staff senior dentist and the roent- The committee was also asked to recom- genograms were taken by the staff NEWBURGH-KINGSTON CARIES-FLUORINE STUDY VOL. 46 267

Table 1-DMF * Teeth per 100 Children Ages 6-16, Based on Clinical and Roentgenographic Examinations, Newburgh t and Kingston, N. Y., 1954-1955

Number of Children Number of DMF Teeth per 100 Children with Permanent Teeth DMF Teeth with Permanent Teeth **

Per cent Difference Age Newburgh Kingston Newburgh Kingston Newburgh Kingston K-N

6- 9 § 708 913 672 2,134 98.4 233.7 - 57.9 10-12 521 640 1,711 4,471 328.1 698.6 - 53.0 13-14 263 441 1,579 5,161 610.1 1,170.3 - 47.9 16 109 119 1,063 1,962 975.2 1,648.7 - 40.9

*DMF includes permanent teeth decayed, missing (lost subsequent to eruption), or filled. t Sodium fluoride added to Newburgh's water supply beginning May 2, 1945. X Age at last birthday at time of examination. ** Adjusted to age distribution of children examined in Kingston who had permanent teeth in the 1954-1955 examination. § Newburgh children of this age group exposed to fluoridated water from time of birth.

senior dentist and dental hygienist. The year-old children in Newburgh was 58 films were developed and sent to the per cent lower than that for the King- Dental Bureau office in Albany. There ston children. The 10- to 12-year-old statisticians randomized the film series children in Newburgh had a DMF rate so that the interpreters did not know 53 per cent lower. At ages 13 to 14 whether they were reading Newburgh the DMF rate was 48 per cent lower, or Kingston films. and at age 16 it was 41 per cent lower, The children aged six through nine than the rates in Kingston (Table 1) - years in Newburgh had used fluoridated The first permanent molar is fre- water throughout their lives. The 10. quently referred to as the keystone of to 12-year-old children, who were under the dental arch and warrants special two years of age in 1945, had used consideration because of its strategic fluoridated water during the partial cal- position in the mouth. This tooth, be- cification of the crowns of the first cause of its morphology and the early permanent molars and throughout the age at which it erupts into the mouth, calcification of the second permanent frequently succumbs to dental caries molar crowns. The 13- to 14-year-old early in life. It is therefore significant children were three to four years old to note that among the six- to nine- in 1945. These children started drink- year-old children in Newburgh the DMF ing fluoridated water after the calcifica- rate for first permanent molars was 53 tion of the crowns of the first molar per cent lower than that for the King- teeth but prior to the eruption of these ston children in the same age group. teeth, and throughout the period of cal- The DMF rate in Newburgh at ages cification of the crowns of the second 10 to 12 was 30 per cent lower, at ages molars. The 16-year-old children were 13 to 14 it was 14 per cent lower, and six years of age when fluoridation was at age 16 it was 4 per cent lower, than started. At that time their first perma- in Kingston (Figure 1) . nent molars were beginning to erupt Of even greater significance is the ob- into the mouth and the crowns of their servation that the children in Newburgh second molars were almost fully cal- at age six to nine had 68 per cent fewer cified. untreated carious first molars and 88 The DMF rate for the six- to nine- per cent fewer first molars lost than did 268 MARCH 1956 AMERICAN JOURNAL OF PUBLIC HEALTH

in both caries detection and correction. Frequently caries on the proximal surface of a tooth requires the cutting of much sound tooth structure in order to place an adequate filling in the tooth. At each of the age levels studied the per cent of differentiable carious proximal surfaces among the Kingston children was about three times greater than that noted in the Newburgh children. At ages six through nine all of the deciduous cuspids and deciduous molars are normally present in the mouth. If Figure 1 any of these teeth are missing it may reasonably be presumed that they were the Kingston children of the same ages. lost because of caries. Among the six- The 10- to 12-year-old children in New- to nine-year-old children in Newburgh burgh had a rate 45 per cent lower for 25.5 per cent had all these teeth present untreated caries and 78 per cent lower and caries free, as compared with 4.7 for missing first molars. At ages 13 to per cent of the Kingston children 14 the differences were 26 per cent for (Table 3). untreated caries and 42 per cent for Dean's 11 epidemiological studies of missing first molars, and at age 16 the endemic dental fluorosis demonstrated differences were 41 per cent for un- that there was no disfiguring dental treated caries and 32 per cent for miss- fluorosis at the level of about 1.0 ppm ing first molars (Table 2). F. Unfortunately, the term mottled Another significant observation was enamel or dental fliorosis is applied to that ingested water fluorides afford se- all degrees of this condition. In its lective protection to the proximal more severe forms it does produce dis- (adjacent) surfaces of the teeth in com- coloring stains and possibly pitting of parison with the occlusal (biting) sur- the enamel. However, in the milder faces. This is highly important because forms of fluorosis the enamel of the the proximal surfaces present difficulties tooth has a high luster which enhances

Table 2-Status of Erupted First Permanent Molars in Children Ages 6-16, Based on Clinical and Roentgenographic Examinations, Newburgh * and Kingston, N. Y., 1954-1955 Per cent of Erupted First Permanent Molars t Caries-Free DMF ** Filled Untreated Caries Missing

Age + Newburgh Kingston Newburgh Kingston Newburgh Kingston Newburgh Kingston Newburgh Kingston

6- 9 § 74.9 46.7 25.1 53.3 14.2 17.8 10.6 33.2 0.3 2.4 10-12 36.8 10.0 63.2 90.0 40.2 41.3 20.5 37.1 2.5 11.6 13-14 19.3 5.9 80.7 94.1 43.9 40.5 27.0 36.7 9.8 16.9 16 8.5 4.8 91.5 95.2 55.0 36.6 20.9 35.5 15.6 23.1 * Sodium fluoride added to Newburgh's water supply beginning May 2, 1945. t Adjusted to the first permanent molar population in the Kingston 1954-1955 examination. Age at last birthday at time of examination. **DMF includes permanent teeth decayed, missing (lost subsequent to eruption), or filled. § Newburgh children of this age group exposed to fluoridated water from time of birth. NEWBURGH-KINGSTON CARIES-FLUORINE STUDY VOL. 46 269

Table 3-Number and Per Cent of Children Age 6-9 with Caries-Free Deciduous Cuspids, First and Second Deciduous Molars, Based on Clinical and Roentgenographic Examinations, Kingston and Newburgh,* N. Y., 1954-1955

Number of Children Per cent Children with Number of Children with All 12 Teeth All 12 Teeth Present Examined Present and Caries Free and Caries-Free

Age t Kingston Newburgh Kingston Newburgh Kingston Newburgh

6 216 184 24 68 11.1 37.0 7 255 208 12 58 4.7 27.9 8 277 213 5 53 1.8 24.9 9 192 129 3 13 1.6 10.1

Total 940 734 44 192 4.7 26.2 Adjusted rate ? 4.7 25.5

* Sodium fluoride added to Newburgh's water supply beginning May 2, 1945. f Age at last birthday at time of examination. Newburgh children of these ages exposed to fluoridated water from time of birth. t Adjusted to the age distribution of Kingston children in the 1954-1955 examination. the beauty of the tooth rather than dis- questionable fluorosis, 26 had very mild, figures it. The detection of the early and six had mild fluorosis. There were signs of dental fluorosis requires an no cases of moderate or severe mottling examiner who has had extensive expe- and in no instance was there any dis- rience in areas of endemic fluorosis. figuring discoloration. Thirty-six of the The average dental practitioner would in Newburgh children examined had non- all probability not detect the earliest fluoride opacities. Of the 612 children signs of mottling. examined in Kingston, 115 had nonfluo- In order to determine whether the ride opacities. The relatively infrequent children in Newburgh showed any occurrence of nonfluoride enamel opaci- signs of dental fluorosis a specially ties in Newburgh compared with King- trained officer of the Public Health ston tends to confirm a previous re- Service with long experience in the de- port 12 that ingested water fluorides at tection of the mildest of such lesions the recommended concentration appear was requested to make the examinations. to reduce the occurrence of hypoplastic He examined 621 children aged seven to spots on the teeth. 14 in Newburgh, of whom 438 had re- The same groups of children exam- sided there continuously since the start ined for enamel opacities were also ex- of fluoridation. In Kingston 612 chil- amined for evidence of gingivitis. A dren of the same ages were examined. positive score was recorded only for In addition to dental fluorosis, examina- flagrant gingivitis, thus making it pos- tions were made for enamel opacities sible to place greater emphasis on ad- due to causes other than ingested fluo- vanced disease and minimize examiner rides. These other enamel opacities are bias. There was slightly, but signifi- generally developmental hypoplasias. cantly, more gingivitis observed among They usually appear as circular white the Kingston children than among those or colored patches and most of them in Newburgh. are obvious even to the untrained eye. The final report on the pediatric find- Among the 438 children with contin- ings of the Newburgh-Kingston study uous residence in Newburgh, 46 had pointed out that all the scientific evi- 270 MARCH 1956 AMERICAN JOURNAL OF PUBLIC HEALTH dence available at the time the study results of these special examinations was first proposed indicated the safety were well within the range of expected of drinking water containing about 1.0 prevalence of the conditions studied. ppm F at the source. There was no Reference was made to another re- reason at that time to believe that fluo- cently published paper 13 which pre- rides, when added to the drinking water sented further evidence for the absence as part of the water treatment process, of systemic effects from flhoridated would act in any way differently from water. The purpose of this study was fluorides already present. Nevertheless, to determine whether any irritative ef- it was considered desirable to test this fects on the kidneys follow prolonged remote possibility under the carefully use of fluoridated water. The quantita- controlled conditions established for the tive excretion of albumin, red blood long-term Newburgh-Kingston study. cells, and casts in 12-hour urine speci- Closely similar groups of children mens in 12-year-old boys, using a modi- were studied in Newburgh and King- fied Addis technic, was determined in ston. In the final year of the study 500 the two cities. The differences in the of the children enrolled in Newburgh results between the groups in the two and 405 in Kingston were examined in cities tended to favor the Newburgh the study clinic. The points of con- children, but no medical significance centration in the examination were those could be attributed to any of the related to possible systemic effects of differences. fluoride ingestion as manifested by The review of current knowledge of changes in growth and development or the metabolism of fluorides, particularly in abnormalities on the physical, labora- in the human body, applied this in- tory, and roentgenographic examina- formation in estimating the factors of tions. Each child was given a general safety in water fluoridation. Knowledge medical examination by a qualified of blood fluoride levels, of the rate and pediatrician. Height and weight were mechanism of urinary excretion of fluo- measured. Roentgenograms were taken ride, and of the magnitude and mecha- of the right hand, both knees, and the nism of bone deposition increases our lumbar spine. Bone density and bone understanding of some important bio- age (maturation of the skeleton) were logical effects of toxic doses of fluorides, estimated by independent observers who such as acute fluoride poisoning, crip- were not aware of the city of origin of pling fluorosis, osteosclerosis, and mot- the individual roentgenograms. Labo- tled enamel. ratory examinations, including hemo- The blood fluoride level in experi- globin level, total leucocyte count, and mental animals given lethal doses of routine urinalysis were also made. No fluoride rises to a peak in a half hour differences of medical significance to an hour, falls rapidly within two could be found between the groups of to three hours, and returns to its normal children in the two cities. This indi- level within 24 hours. The blood does cated the absence of any findings sug- not tend to accumulate fluoride, al- gestive of systemic effects from the though the blood fluoride level in per- drinking of fluoridated water during the sons drinking fluoridated water is some- period of most rapid growth. In ad- what higher than in persons drinking dition, special detailed studies of the fluoride-deficient water. eyes and ears were performed on a When human beings ingest small smaller group of children; these in- amounts of fluoride a significant frac- cluded determination of visual acuity, tion is promptly excreted in the urine. visual fields, and hearing levels. The It is probable that when human beings NEWBURGH-KINGSTON CARIES-FLUORINE STUDY VOL. 46 271

ingest small amounts of fluoride equiva- available to indicate no influence of lent to that of fluoridated water over a fluoride intake on any of these at the period of years, the daily urinary excre- levels found in any water supplies in tion is greater than half of the amount the United States. Studies on experi- absorbed each day. The extraordinarily mental animals with the use of radio- rapid and efficient urinary excretion of active fluoride show that the thyroid fluoride is attributable to a somewhat gland does not concentrate fluoride as lower resorption of fluoride in the kid- it does iodide. The presence of renal ney tubules than is characteristic of impairment in experimental animals and chloride. in human beings with long-standing The other mechanism for removal of kidney disease appears not to affect fluoride from the blood is by deposition excretion of fluoride by the kidneys. in the bones, the amount of fluoride The comprehensive analysis of present in the hard tissues probably the Newburgh-Kingston Caries-Fluorine being directly dependent on the amount Study after 10 years of experience, of fluoride taken into the body day after added to the wealth of evidence pre- day. The mechanism of fluoride deposi- viously reported, demonstrates conclu- tion is simple, the fluoride ion replacing sively two important facts-fluoridation the hydroxyl groups of the surface of is effective in reducing dental caries and the bone crystals. There is no indica- it is a safe public health practice. tion that any notable biological disad- vantage results from this. Fluoride deposition in bone is a reversible REFERENCES process. 1. Dean, H. T.; Arnold, F. A.; and Elvove, E. Domestic Water and Dental Caries. Pub. Health With regard to acute fluoride poison- Rep. 57:1155, 1942. ing 2. Russell, A. L., and Elvove, E. Domestic Water and there is at least a 2,500-fold factor Dental Caries: VII. A Study of the Fluoride-dental of safety in water Caries Relationship in an Adult Population. Ibid. fluoridation. The 66:1389, 1951. mechanics of water fluoridation are 3. Dean, H. T. Fluorine in the Control of Dental such that it is impossible to produce Caries. J. Am. Dent. A. 52:1, 1956. 4. Hilleboe, H. E. History of the Newburgh-Kingston acute fluoride poisoning either by acci- Caries Fluorine Study. Ibid. Vol. 57 (Mar.), 1956. dent or intent. 5. Schlesinger, E. R., et al. The Newburgh-Kingston Caries-Fluorine Study: XIII. Pediatric Findings Crippling fluorosis, characterized by After Ten Years. Ibid. Vol. 57 (Mar.), 1956. a stiffening in the back due to calcifica- 6. Ast, D. B., et al. The Newburgh-Kingston Caries- Fluorine Study: XIV. Combined Clinical and tion of the broad ligaments of the back, Roentgenographic Dental Findings After Ten Years of Fluoride Experience. Ibid. Vol. 57 (Mar.), occurs with a daily intake of 20 to 80 1956. milligrams of flhoride or more for 10 to 7. Hodge, H. C. Fluoride Metabolism: Its Significance 20 years. Since five gallons of fluori- in Water Fluoridation. Ibid. Vol. 57 (Mar.), 1956. 8a. Moulton, F. R., editor. Fluorine and Dental dated water at 1 ppm F contain 20 Health. Washington, D. C.: American Association milligrams, it is obvious for the Advancement of Science, 1942. that crippling 8b. . Dental Caries and Fluorine. Washington, fluorosis can never be produced by D. C.: American Association for the Advancement drinking of Science, 1946. fluoridated water. The earliest 9. Cox, G. J.; Matuschak, M. C.; et al. Experimental evidence of osteosclerosis, a hypercalci- Dental Caries IV. Fluorine and Its Relation to fication Dental Caries. J. Dent. Res. 18:481, 1939. detectable by roentgen examina- 10. Ast, D. B. The Caries-Fluorine Hypothesis and A tion, does not occur with an intake of Suggested Study to Test Its Application. Pub. Health Rep. 58:857, 1943. fluoride below eight to 10 times the level I1. Dean, H. T. Endemic Fluorosis and Its Relation. of fluoridated water. to Dental Caries. Ibid. 53:1443, 1938. 12. Zimmerman, E. R. Fluoride and Nonfluoride The evidence with respect to heart Enamel Opacities. Ibid. 69:1115, 1954. disease, kidney disease, cancer, and pos- 3. Schlesinger, E. R.; Overton, D. E.; and Chase, H. C. Study of Children Drinking Fluoridated and sible influence of fluoride on the thyroid Nonfluoridated Water: Quantitative Urinary Excre- is also tion of Albumin and Formed Elements. J.A.M.A. reviewed. Ample statistics are 160:21, 1956.