In 1968 at Seagrove, NC, flu o rid e was a d d ed to the w ater supply of a ru ra l school (grades 1 through 12) at a lev el o f 6.3 ppm , seven times the optimum lev el reco m m en d ed fo r community w ater fluoridation in the area. Findings a fter eight y ea rs show ed that children in gra des 1 through 8 h a d approxim ately 40% fe w e r DM F su rfaces than did their counterparts on the baseline. A comparison of these fin dings with those o f another school fluoridation study, in which a lev el o f 4 .5 times the optimum concentration h a d b een tested, show ed only a slight advantage to the children at Seagrove. However, the fu ll potential of school w ater fluoridation at seven times the optimum level cannot b e determ in ed until children in all gra d es will h av e b een exp o sed since entering the first gra de.
Effect of school water fluoridation on dental caries: results in Seagrove, NC, after eight years
Stanley B. Heifetz, DDS, MPH H erschel S. Horowitz, DDS, MPH W illiam S. Driscoll, DDS, MPH, Seagrove, NC
c
hildren who live in regions where water is supplied through w ells, cisterns, or other in d i vidual water sources that have essentially no fluorides cannot obtain the decay-preventive ben e fits of drinking com m unity water that has been optim ally fluoridated. Currently, approxim ately 23% of the population of the U nited States lives in regions that lack central water system s.1 In other countries, the proportion of the population not supplied by centralized w ater sources is usually greater. Because com m unity fluoridation is not possible for a large segm ent of the w orld’s popula tion, alternative m ethods for w ide-scale preven tion of dental caries have been studied. One m ethod that has consistently reduced the preva len ce of dental caries is the addition of fluoride to sch o o ls’ w ater supplies at levels higher than the concentration recom m ended for com m unity fluoridation in the same geographic region .2 6 A higher concentration of fluoride is used because children consum e only part of their daily intake of water at school. The com plete rationale for fluori
dation of sch ools’ water supplies has been ex plained in previous pu blication s.2,4,6 Currently, on the basis of results of a 12-year study of flu ori dated w ater in a school in Elk Lake, P a,5 a level of 4.5 tim es the concentration of fluoride that would be used for fluoridation of the com m unity’s water can be recom m ended as safe and effective for fluoridation of water in schools in the sam e geog raphic region. However, the m ost effective ratio of fluoridation of water supplies in schools in rela tion to fluoridation of com m unity water supplies has not been clearly established. To help provide some of this inform ation, a 12-year study was in i tiated in 1968 in Seagrove, NC. At Seagrove school, fluoride was added to the water supply at a concentration of 6.3 ppm , seven tim es the optimum level recom m ended for com m unity water fluoridation in that geographic re gion.7,8 T h is paper contains interim findings of the effectiveness and safety of fluoridation of water in the school in Seagrove after eight years of study and com pares these results w ith corre JADA, Vol. 97, August 1978 ■ 193
sponding data collected after eight years, from Elk Lake, Pa, where fluoridation of water in the school was conducted at 4.5 tim es the optimum concen tration.
Study procedures Children who attend the Seagrove school live in a rural com m unity that is not served by a central water supply. Analysis of specim ens of water col lected from the school’s well and from a sampling of wells in the school attendance area showed that the drinking water contained minimal levels of fluoride (0.3 ppm or less). During the summer of 1968, fluoridation equipment designed to add 6.3 ppm of fluoride was installed in the school’s water system. School personnel were trained to operate and maintain the fluoridation unit under the supervision of the Dental Health Section, Division of Health Services, state of North Carolina. Tech nical consultation is provided by the Water Sup ply Division of the Environmental Protection Agency. Fluoride levels maintained in the school’s drinking w ater are surveyed by running split-sample analyses tw ice a week; one portion is analyzed at the school, and the other is mailed to the Division of Health Services’ laboratory for in dependent analysis. To encourage students to drink water at school, several water coolers were installed in the hallways. In addition, the kitchen staff is encouraged to serve foods that require pre paration with water, such as soups, juices, and gelatin desserts. Before the equipment was installed in May 1968, baseline dental examinations were made of approxim ately 1,100 students enrolled in grades 1 through 12 at the school. A DMFS assessment was made by three public health dentists who used well-defined, visual-tactile criteria.9 Follow-up examinations to determine the interim effects of the procedure were conducted in May 1972 and 1976. Findings of the 1972 survey have been re ported.10 At the 1976 survey, examinations for dental caries were made by two dentists from the Public Health Service (PHS), one of whom had participated in all previous examinations. A t the start of each survey, the examiners standardized their interpretation of diagnostic criteria; they cal ibrated their examining techniques daily during the exam ination period. The 1976 survey also in cluded an exam ination for dental fluorosis. De terminations for fluorosis, according to standards described by Dean,11 were m ade by a third PHS dentist. 194 ■ JADA, Vol. 97, August 1978
Findings During the first eight years of study, 516 samples of water were analyzed at the state’s laboratory. There was some variation from year to year in both frequency of sampling and average fluoride levels maintained. However, in no year were fewer than 54 samples analyzed nor did the average fluoride concentration fall below 6.14 ppm. The average of the yearly levels of fluoride was 6.59 ppm, slightly higher than the target level of 6.30 ppm. At the 1976 examinations, children in grades 1 through 8 who had been exposed continuously to fluoridated water at school since the first grade (usually from 6 years of age) should show the m aximal benefits. Data were collected, therefore, for children aged 6 through 14 (grades 1 through 8) who had always attended Seagrove school. A few children who had a record of continuous at tendance since entering the school belatedly at ages 7 or 8 were also included in the follow-up survey. Findings for 646 children at the 1976 exam ina tions and 630 at the baseline examinations who met the same age and school residency require ments are shown in Table 1. Mean DMF surface scores for each age group in 1976 were lower than the corresponding scores at the baseline. Differ ences in caries prevalence in 1976 com pared with 1968 generally increased with age, ranging widely from approxim ately a third of a DMF surface (6year-old children) to approxim ately nine fewer (14-year-old children) DMF surfaces per child. There was no trend, however, of the percentage differences with age. After eight years of fluori dated water at school, the total study population had an average of 5.48 DMF surfaces. In com pari son, their fellow students on the baseline had av eraged 9.08 DMF surfaces, a difference of 3.6 sur faces per child, or 39.6% . Table 2 shows com parative interim findings for children 6 through 14 years of age at Seagrove, NC, and at Elk Lake, Pa, after eight years of fluori dated water at school. M ean DMF surface scores for all ages combined at Seagrove, shown in Ta bles 1 and 2, do not agree exactly because it was necessary to use different reference populations for adjusting crude findings. The two sets of data show only a small difference in the overall meas urement of caries inhibition conferred by fluori dated water at school at 4 .5 and seven times the optimum concentration. Compared with baseline findings, children at Elk Lake showed a 34.9% dif
Table 1 ■ Average DMF surface scores by age in 1968 and 1976, Seagrove, N.C. 1968 (Baseline) 1976 No. Average No. Average children no. DMFS children no DMFS Age 646 Total 630 9.08 5.48 6 27 1.07 38 0.71 7 76 2.29 96 1.40 8 79 3.86 68 2.06 9 89 5.69 80 3.28 10 78 7.91 96 6.04 11 74 90 10.26 6.93 12 82 77 14.23 7.10 15.21 72 9.22 13 63 14 51 21.82 40 12.68 ‘ Adjusted to baseline age distribution.
ference in m ean DMF surfaces; after eight years at Seagrove, the corresponding benefit was slightly greater, a 39.7% difference. Similarly, children who consum ed water with the higher concentra tion of fluoride derived only slightly greater actual protection from dental decay (approxim ately xk of a DMF surface per child) than at the lower concen tration. Continuous participants in grades 7 and 8 were examined for dental fluorosis. Canines, premolars, and second m olars of these children had received maxim al possible exposure to the higher fluoride levels at school while their teeth were still calcify ing. If the procedure caused fluorosis, these teeth, now largely erupted in children 13 and 14 years old, could best show it. A total of 134 children were exam ined for dental fluorosis. None showed any definite signs of the condition. Eleven chil dren (8.2% ) were classified as having questionable fluorosis, and the rem ainder were classified as normal.
Difference in average % difference from 1968 no. DMFS -3.60 -39.6 -33.6 -0.36 -0.89 -39.0 -46.7 -1.80 -2.42 -42.4 -23.6 -1.87 -32.4 -3.33 -50.1 -7.13 -5.99 -39.4 -41.9 -9.15
Discussion and conclusion Findings after eight years of study corroborate ear lier interim results reported on the effectiveness of fluoridation of the school’s water supply at Sea grove. Whereas children 6 through 14 years of age who were full beneficiaries of the procedure in 1976 showed approxim ately a 40% difference in caries inhibition, children 6 through 10 years of age who were the full beneficiaries at the time of the 1972 follow-up survey showed about a 30% difference in average DMF surfaces. An im prove m ent in benefits as the study progressed had been anticipated because findings in 1972 were based alm ost entirely on effects in early erupting teeth (incisors and first molars). The relative effective ness of fluoridation of water at school is approxi m ately tw ice as great in late-erupting teeth (canines, premolars, and second molars) that re ceive both system ic and topical exposure to fluoride than in early-erupting teeth that primarily
Table 2 ■ Average DMF surface scores by age on baseline and after eight years of fluoridated water at school. 1976
1968 (Baseline) Age Seagrove, NC Total 6 7 8 9 10 11 12 13 14
No. children
27 76 79 89 78 90 77 63 51
Average no. DMFS 9.34* 1.07 2.29 3.86 5.6Ô 7.91. 10.26 14.23 15.21 21.82
No. children
38 96 68 80 96 74 82 72 40
Elk Lake, Pa 9.86* Total 109 1.00 6 91 106 84 2.77 7 64 4.33 98 8 5.92 114 9 85 7.72 79 10 81 103 10.15 11 123 15.73 90 12 90 18.12 88 13 114 20.81 93 14 85 ‘ Adjusted to combined baseline age distributions of both schools.
Average no. DMFS
Difference in average no. DMFS
% difference from baseline
5.63* 0.71 1.40 2.06 3.28 6.04 6.93 7.10 9.22 12.68
-3.71 -0.36 -0.89 -1.80 -2.42 -1.87 -3.33 -7.13 -5.99 -9.15
-39.7 -33.6 -39.0 -46.7 -42.4 -23.6 -32.4 -50.1 -39.4 -41.9
6.42* 0.35 1.30 2.44 4.31 6.01 7.25 9.93 10.53 14.16
-3.44 -0.65 -1.47 -1.89 -1.61 -1.71 -2.90 -5.80 -7.59 -6.65
-34.9 -65.0 -53.1 -43.7 - 27.2 22.2 -28.6 -36.9 -41.9 -32.0
Heifetz—Horowitz—Driscoll: EIGHT-YEAR STUDY ON SCHOOL WATER FLUORIDATION ■ 195
receive only topical b en efits.5 At the tim e of the 1976 survey, about 15% of the total caries preva len ce was derived from late-erupting teeth. B en e fits at the fin al exam inations in 1980 may exceed the 40% in h ib itio n in dental caries observed after eight years of study because findings on 15-, 16-, and 17-year-old ch ild ren w ill be includ ed in the analysis. Late-erupting teeth of these oldest par ticip ants should have the greatest potential for show ing protection. Flu orid ation of the sch ool’s water supply at seven tim es the optim um concentration did not produce any signs of dental fluorosis. B ecause fluorosis is a developm ental disturbance that can be produced only at the in itial stage of enam el m atrix form ation and m ineralization, the form a tive state of teeth of children of school age (ex cepting third molars) may be too advanced to be affected adversely by exposure to higher levels of fluoride. E pidem iologic findings tend to support this hypothesis. Data co llected from a 1928 survey of ch ild ren in B auxite, Ark, who drank water at school that contained fluoride at a concentration of 13.7 ppm but who consum ed water at hom e that had in sig n ifican t am ounts of fluoride showed that the child ren had norm al enam el.12 A lthough the study is still in progress, the cur rent find ings suggest that fluoridation of water at school at the level of seven tim es the optim um concen tration that would be recom m ended for com m unity fluoridation in the same region con fers only m arginally greater in h ib itio n of dental caries than at 4.5 tim es the optimum level. Com pared w ith participants at Elk Lake, full be neficiaries of sch ool fluoridation at Seagrove show ed the sam e decrease in average caries preva len ce after eight years as did full beneficiaries after four years (approxim ately xk of a DMF sur face per child). If com parative data at the final exam inations continue to parallel interim fin d
ings, there would be no scien tific rationale for using fluoride concentrations in school water supplies greater than the currently recom m ended 4.5 tim es the optimum level.
The authors thank Dr. R. Young and Mr. C. E. Pitts, Dental Health Section, Division of Services, North Central Regional Office, state of North Carolina, for supervising the operation of the school fluoridation system. The informed consent and concurrence of all appropriate school and health officials responsible for the health and well-being of human sub jects who participated in the experim ental investigation reported or de scribed in this m anuscript were obtained after the nature of the proce dures and possible discomforts and risks had been fully explained. I . The United States and Environmental Protection Agency’s con tribution to an adequate supply of safe drinking water for all Americans. W ashington, Govt Print Off, 1972. 2 Horowitz, H.S.; Law, F.E.; and Pritzker, T. Effect of school water fluoridation on dental caries, St. Thom as, VI. Public Health Rep 80:381 May 1965. 3. Horowitz, H .S.; Heifetz, S.B.; and Law, F.E. School fluoridation studies in Elk Lake, Pennsylvania, and Pike County, Kentucky: interim report. JADA 71:1124 Nov 1965. 4. Horowitz, H.S., and others. School fluoridation studies in Elk Lake, Pennsylvania, and Pike County, Kentucky— results after eight years. Am J Public Health 58:2240 Dec 1968. 5. Horowitz, H.S.; Heifetz, S.B.; and Law, F.E. Effect of school water fluoridation on dental caries: final results in Elk Lake, Pa, after 12 years. JADA 84:832 April 1972. 6. Horowitz, H.S. School fluoridation for the prevention of dental caries. Int Dent J 23:346 June 1973. 7. US Department of Commerce, Weather Bureau. Climatic summary of United States, suppl for 1951-60. Climatography of United States, no. 86-27, North Carolina. W ashington, Govt Print Off, 1965, p 60. 8. US Public Health Service. Public Health Service drinking water standards, no. 956. W ashington, Govt Print Off, 1962, p 8. 9. Am erican Dental A ssociation, Council on Dental Research and Therapeutics. Proceedings of the conference on the clinical testing of cariostatic agents. Chicago, Am erican Dental Association, 1972. 10. Heifetz, S.B., and Horowitz, H.S. Effect of school water fluorida tion on dental caries: interim results in Seagrove, NC, after four years. JADA 88:352 Feb 1974. I I . Dean, H.T. The investigation of physiological effects by the epidem iological methods. In F.R. Moulton (ed.), Fluorine and dental health. W ashington, Am erican Association for the Advancement of Sci ence, 1942, pp 23-31. 12. Kempf, G.A., and McKay, F.S. Mottled enamel in a segregated population. Public Health Rep 45:2923 Nov 1930.
THE AU TH ORS
Drs. Heifetz, Horowitz, and Driscoll work in the Caries Preven tion and Research Branch, National Institutes of Health, Public Health Service, U S Department of Health, Education, and Welfare, Westwood Bldg, Bethesda, Md 20014. Address requests for reprints to Dr. Heifetz.
H E IFE T Z
196 ■ JADA, Vol. 97, August 1978
H O R O W IT Z
D R ISC O L L
Effect of school water fluoridation on dental caries: results in Seagrove, NC, after eight years
Stanley B. Heifetz, DDS, MPH H erschel S. Horowitz, DDS, MPH W illiam S. Driscoll, DDS, MPH, Seagrove, NC
c
hildren who live in regions where water is supplied through w ells, cisterns, or other in d i vidual water sources that have essentially no fluorides cannot obtain the decay-preventive ben e fits of drinking com m unity water that has been optim ally fluoridated. Currently, approxim ately 23% of the population of the U nited States lives in regions that lack central water system s.1 In other countries, the proportion of the population not supplied by centralized w ater sources is usually greater. Because com m unity fluoridation is not possible for a large segm ent of the w orld’s popula tion, alternative m ethods for w ide-scale preven tion of dental caries have been studied. One m ethod that has consistently reduced the preva len ce of dental caries is the addition of fluoride to sch o o ls’ w ater supplies at levels higher than the concentration recom m ended for com m unity fluoridation in the same geographic region .2 6 A higher concentration of fluoride is used because children consum e only part of their daily intake of water at school. The com plete rationale for fluori
dation of sch ools’ water supplies has been ex plained in previous pu blication s.2,4,6 Currently, on the basis of results of a 12-year study of flu ori dated w ater in a school in Elk Lake, P a,5 a level of 4.5 tim es the concentration of fluoride that would be used for fluoridation of the com m unity’s water can be recom m ended as safe and effective for fluoridation of water in schools in the sam e geog raphic region. However, the m ost effective ratio of fluoridation of water supplies in schools in rela tion to fluoridation of com m unity water supplies has not been clearly established. To help provide some of this inform ation, a 12-year study was in i tiated in 1968 in Seagrove, NC. At Seagrove school, fluoride was added to the water supply at a concentration of 6.3 ppm , seven tim es the optimum level recom m ended for com m unity water fluoridation in that geographic re gion.7,8 T h is paper contains interim findings of the effectiveness and safety of fluoridation of water in the school in Seagrove after eight years of study and com pares these results w ith corre JADA, Vol. 97, August 1978 ■ 193
sponding data collected after eight years, from Elk Lake, Pa, where fluoridation of water in the school was conducted at 4.5 tim es the optimum concen tration.
Study procedures Children who attend the Seagrove school live in a rural com m unity that is not served by a central water supply. Analysis of specim ens of water col lected from the school’s well and from a sampling of wells in the school attendance area showed that the drinking water contained minimal levels of fluoride (0.3 ppm or less). During the summer of 1968, fluoridation equipment designed to add 6.3 ppm of fluoride was installed in the school’s water system. School personnel were trained to operate and maintain the fluoridation unit under the supervision of the Dental Health Section, Division of Health Services, state of North Carolina. Tech nical consultation is provided by the Water Sup ply Division of the Environmental Protection Agency. Fluoride levels maintained in the school’s drinking w ater are surveyed by running split-sample analyses tw ice a week; one portion is analyzed at the school, and the other is mailed to the Division of Health Services’ laboratory for in dependent analysis. To encourage students to drink water at school, several water coolers were installed in the hallways. In addition, the kitchen staff is encouraged to serve foods that require pre paration with water, such as soups, juices, and gelatin desserts. Before the equipment was installed in May 1968, baseline dental examinations were made of approxim ately 1,100 students enrolled in grades 1 through 12 at the school. A DMFS assessment was made by three public health dentists who used well-defined, visual-tactile criteria.9 Follow-up examinations to determine the interim effects of the procedure were conducted in May 1972 and 1976. Findings of the 1972 survey have been re ported.10 At the 1976 survey, examinations for dental caries were made by two dentists from the Public Health Service (PHS), one of whom had participated in all previous examinations. A t the start of each survey, the examiners standardized their interpretation of diagnostic criteria; they cal ibrated their examining techniques daily during the exam ination period. The 1976 survey also in cluded an exam ination for dental fluorosis. De terminations for fluorosis, according to standards described by Dean,11 were m ade by a third PHS dentist. 194 ■ JADA, Vol. 97, August 1978
Findings During the first eight years of study, 516 samples of water were analyzed at the state’s laboratory. There was some variation from year to year in both frequency of sampling and average fluoride levels maintained. However, in no year were fewer than 54 samples analyzed nor did the average fluoride concentration fall below 6.14 ppm. The average of the yearly levels of fluoride was 6.59 ppm, slightly higher than the target level of 6.30 ppm. At the 1976 examinations, children in grades 1 through 8 who had been exposed continuously to fluoridated water at school since the first grade (usually from 6 years of age) should show the m aximal benefits. Data were collected, therefore, for children aged 6 through 14 (grades 1 through 8) who had always attended Seagrove school. A few children who had a record of continuous at tendance since entering the school belatedly at ages 7 or 8 were also included in the follow-up survey. Findings for 646 children at the 1976 exam ina tions and 630 at the baseline examinations who met the same age and school residency require ments are shown in Table 1. Mean DMF surface scores for each age group in 1976 were lower than the corresponding scores at the baseline. Differ ences in caries prevalence in 1976 com pared with 1968 generally increased with age, ranging widely from approxim ately a third of a DMF surface (6year-old children) to approxim ately nine fewer (14-year-old children) DMF surfaces per child. There was no trend, however, of the percentage differences with age. After eight years of fluori dated water at school, the total study population had an average of 5.48 DMF surfaces. In com pari son, their fellow students on the baseline had av eraged 9.08 DMF surfaces, a difference of 3.6 sur faces per child, or 39.6% . Table 2 shows com parative interim findings for children 6 through 14 years of age at Seagrove, NC, and at Elk Lake, Pa, after eight years of fluori dated water at school. M ean DMF surface scores for all ages combined at Seagrove, shown in Ta bles 1 and 2, do not agree exactly because it was necessary to use different reference populations for adjusting crude findings. The two sets of data show only a small difference in the overall meas urement of caries inhibition conferred by fluori dated water at school at 4 .5 and seven times the optimum concentration. Compared with baseline findings, children at Elk Lake showed a 34.9% dif
Table 1 ■ Average DMF surface scores by age in 1968 and 1976, Seagrove, N.C. 1968 (Baseline) 1976 No. Average No. Average children no. DMFS children no DMFS Age 646 Total 630 9.08 5.48 6 27 1.07 38 0.71 7 76 2.29 96 1.40 8 79 3.86 68 2.06 9 89 5.69 80 3.28 10 78 7.91 96 6.04 11 74 90 10.26 6.93 12 82 77 14.23 7.10 15.21 72 9.22 13 63 14 51 21.82 40 12.68 ‘ Adjusted to baseline age distribution.
ference in m ean DMF surfaces; after eight years at Seagrove, the corresponding benefit was slightly greater, a 39.7% difference. Similarly, children who consum ed water with the higher concentra tion of fluoride derived only slightly greater actual protection from dental decay (approxim ately xk of a DMF surface per child) than at the lower concen tration. Continuous participants in grades 7 and 8 were examined for dental fluorosis. Canines, premolars, and second m olars of these children had received maxim al possible exposure to the higher fluoride levels at school while their teeth were still calcify ing. If the procedure caused fluorosis, these teeth, now largely erupted in children 13 and 14 years old, could best show it. A total of 134 children were exam ined for dental fluorosis. None showed any definite signs of the condition. Eleven chil dren (8.2% ) were classified as having questionable fluorosis, and the rem ainder were classified as normal.
Difference in average % difference from 1968 no. DMFS -3.60 -39.6 -33.6 -0.36 -0.89 -39.0 -46.7 -1.80 -2.42 -42.4 -23.6 -1.87 -32.4 -3.33 -50.1 -7.13 -5.99 -39.4 -41.9 -9.15
Discussion and conclusion Findings after eight years of study corroborate ear lier interim results reported on the effectiveness of fluoridation of the school’s water supply at Sea grove. Whereas children 6 through 14 years of age who were full beneficiaries of the procedure in 1976 showed approxim ately a 40% difference in caries inhibition, children 6 through 10 years of age who were the full beneficiaries at the time of the 1972 follow-up survey showed about a 30% difference in average DMF surfaces. An im prove m ent in benefits as the study progressed had been anticipated because findings in 1972 were based alm ost entirely on effects in early erupting teeth (incisors and first molars). The relative effective ness of fluoridation of water at school is approxi m ately tw ice as great in late-erupting teeth (canines, premolars, and second molars) that re ceive both system ic and topical exposure to fluoride than in early-erupting teeth that primarily
Table 2 ■ Average DMF surface scores by age on baseline and after eight years of fluoridated water at school. 1976
1968 (Baseline) Age Seagrove, NC Total 6 7 8 9 10 11 12 13 14
No. children
27 76 79 89 78 90 77 63 51
Average no. DMFS 9.34* 1.07 2.29 3.86 5.6Ô 7.91. 10.26 14.23 15.21 21.82
No. children
38 96 68 80 96 74 82 72 40
Elk Lake, Pa 9.86* Total 109 1.00 6 91 106 84 2.77 7 64 4.33 98 8 5.92 114 9 85 7.72 79 10 81 103 10.15 11 123 15.73 90 12 90 18.12 88 13 114 20.81 93 14 85 ‘ Adjusted to combined baseline age distributions of both schools.
Average no. DMFS
Difference in average no. DMFS
% difference from baseline
5.63* 0.71 1.40 2.06 3.28 6.04 6.93 7.10 9.22 12.68
-3.71 -0.36 -0.89 -1.80 -2.42 -1.87 -3.33 -7.13 -5.99 -9.15
-39.7 -33.6 -39.0 -46.7 -42.4 -23.6 -32.4 -50.1 -39.4 -41.9
6.42* 0.35 1.30 2.44 4.31 6.01 7.25 9.93 10.53 14.16
-3.44 -0.65 -1.47 -1.89 -1.61 -1.71 -2.90 -5.80 -7.59 -6.65
-34.9 -65.0 -53.1 -43.7 - 27.2 22.2 -28.6 -36.9 -41.9 -32.0
Heifetz—Horowitz—Driscoll: EIGHT-YEAR STUDY ON SCHOOL WATER FLUORIDATION ■ 195
receive only topical b en efits.5 At the tim e of the 1976 survey, about 15% of the total caries preva len ce was derived from late-erupting teeth. B en e fits at the fin al exam inations in 1980 may exceed the 40% in h ib itio n in dental caries observed after eight years of study because findings on 15-, 16-, and 17-year-old ch ild ren w ill be includ ed in the analysis. Late-erupting teeth of these oldest par ticip ants should have the greatest potential for show ing protection. Flu orid ation of the sch ool’s water supply at seven tim es the optim um concentration did not produce any signs of dental fluorosis. B ecause fluorosis is a developm ental disturbance that can be produced only at the in itial stage of enam el m atrix form ation and m ineralization, the form a tive state of teeth of children of school age (ex cepting third molars) may be too advanced to be affected adversely by exposure to higher levels of fluoride. E pidem iologic findings tend to support this hypothesis. Data co llected from a 1928 survey of ch ild ren in B auxite, Ark, who drank water at school that contained fluoride at a concentration of 13.7 ppm but who consum ed water at hom e that had in sig n ifican t am ounts of fluoride showed that the child ren had norm al enam el.12 A lthough the study is still in progress, the cur rent find ings suggest that fluoridation of water at school at the level of seven tim es the optim um concen tration that would be recom m ended for com m unity fluoridation in the same region con fers only m arginally greater in h ib itio n of dental caries than at 4.5 tim es the optimum level. Com pared w ith participants at Elk Lake, full be neficiaries of sch ool fluoridation at Seagrove show ed the sam e decrease in average caries preva len ce after eight years as did full beneficiaries after four years (approxim ately xk of a DMF sur face per child). If com parative data at the final exam inations continue to parallel interim fin d
ings, there would be no scien tific rationale for using fluoride concentrations in school water supplies greater than the currently recom m ended 4.5 tim es the optimum level.
The authors thank Dr. R. Young and Mr. C. E. Pitts, Dental Health Section, Division of Services, North Central Regional Office, state of North Carolina, for supervising the operation of the school fluoridation system. The informed consent and concurrence of all appropriate school and health officials responsible for the health and well-being of human sub jects who participated in the experim ental investigation reported or de scribed in this m anuscript were obtained after the nature of the proce dures and possible discomforts and risks had been fully explained. I . The United States and Environmental Protection Agency’s con tribution to an adequate supply of safe drinking water for all Americans. W ashington, Govt Print Off, 1972. 2 Horowitz, H.S.; Law, F.E.; and Pritzker, T. Effect of school water fluoridation on dental caries, St. Thom as, VI. Public Health Rep 80:381 May 1965. 3. Horowitz, H .S.; Heifetz, S.B.; and Law, F.E. School fluoridation studies in Elk Lake, Pennsylvania, and Pike County, Kentucky: interim report. JADA 71:1124 Nov 1965. 4. Horowitz, H.S., and others. School fluoridation studies in Elk Lake, Pennsylvania, and Pike County, Kentucky— results after eight years. Am J Public Health 58:2240 Dec 1968. 5. Horowitz, H.S.; Heifetz, S.B.; and Law, F.E. Effect of school water fluoridation on dental caries: final results in Elk Lake, Pa, after 12 years. JADA 84:832 April 1972. 6. Horowitz, H.S. School fluoridation for the prevention of dental caries. Int Dent J 23:346 June 1973. 7. US Department of Commerce, Weather Bureau. Climatic summary of United States, suppl for 1951-60. Climatography of United States, no. 86-27, North Carolina. W ashington, Govt Print Off, 1965, p 60. 8. US Public Health Service. Public Health Service drinking water standards, no. 956. W ashington, Govt Print Off, 1962, p 8. 9. Am erican Dental A ssociation, Council on Dental Research and Therapeutics. Proceedings of the conference on the clinical testing of cariostatic agents. Chicago, Am erican Dental Association, 1972. 10. Heifetz, S.B., and Horowitz, H.S. Effect of school water fluorida tion on dental caries: interim results in Seagrove, NC, after four years. JADA 88:352 Feb 1974. I I . Dean, H.T. The investigation of physiological effects by the epidem iological methods. In F.R. Moulton (ed.), Fluorine and dental health. W ashington, Am erican Association for the Advancement of Sci ence, 1942, pp 23-31. 12. Kempf, G.A., and McKay, F.S. Mottled enamel in a segregated population. Public Health Rep 45:2923 Nov 1930.
THE AU TH ORS
Drs. Heifetz, Horowitz, and Driscoll work in the Caries Preven tion and Research Branch, National Institutes of Health, Public Health Service, U S Department of Health, Education, and Welfare, Westwood Bldg, Bethesda, Md 20014. Address requests for reprints to Dr. Heifetz.
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196 ■ JADA, Vol. 97, August 1978
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