Dietary Fluoride Research Articles

The case for eliminating the use of dietary fluoride supplements for young children.

Fluoride supplements have been used for years to prevent dental caries; nevertheless, there are three reasons why their use is inappropriate today among infants and young children in the United States. Evidence for the efficacy of fluoride supplements when used from birth or soon after is weak, supplements are a risk factor for dental fluorosis, and fluoride has little preeruptive effect in caries prevention. While there are many reports on the caries-preventive efficacy of supplements, few meet standards for acceptability as clinical trials, and those that do have tested chewable tablets or lozenges under supervision in school-aged children. North American children today are exposed to fluoride from many sources--drinking water, toothpaste, gels, rinses, and in processed foods and beverages. The additional cariostatic benefits that accrue from using supplements are marginal at best, while there is strong risk of fluorosis when young children use supplements. Available evidence suggests that the public is more aware of the milder forms of fluorosis than was previously thought; thus, it is prudent for caries-preventive policies to aim to maximizing caries reductions while minimizing the risk of fluorosis. It is therefore concluded that the risks of using supplements in infants and young children outweigh the benefits. Because alternative forms of fluoride for high-risk individuals exist, fluoride supplements should no longer be used for young children in North America.

Challenges of and Strategies for Changing Prescribing Practices of Health Care Providers

Problems related to inappropriate prescribing practices of physicians in general are well recognized. Dietary fluoride supplements have been implicated as one of the contributing factors in an increase in dental fluorosis. Inappropriate prescribing practices of providers have been cited as a major factor in this implication. Numerous studies of physicians and dentists have documented a lack of knowledge and inappropriate prescribing practices regarding fluoride supplements. The purpose of this paper is to identify barriers to changing fluoride-prescribing practices of health care providers and to suggest strategies for implementing change. To increase optimal and appropriate use of fluoride supplements, educational interventions are necessary for all user groups--detail men and women, physicians, dentists, pharmacists, nurse practitioners, dental hygienists, and the public. In addition, environmental supports for the educational activities in the form of policy, regulation, standards of care, and guidelines are recommended for consideration.

ASSESSING FLUORIDE LEVELS OF CARBONATED SOFT DRINKS

Dental fluorosis occurs as a result of excessive total fluoride intake during tooth development. Some children may receive substantial intake from soft drinks, but few studies have reported fluoride levels in soft drinks. The authors examined the fluoride concentrations of 332 soft drinks. Soft drinks were purchased from Iowa grocery stores. To identify production sites, the authors recorded product details and batch numbers. After decarbonating the drinks, the authors assayed samples for fluoride content using a fluoride ion-specific electrode, and reported the results in parts per million, or ppm, using appropriate standards and duplicate assessments. Descriptive statistics were used to summarize the findings. The fluoride levels of the products ranged from 0.02 to 1.28 ppm, with a mean level of 0.72 ppm. Fluoride levels exceeded 0.60 ppm for 71 percent of the products. Results varied substantially by production site, even within the same company and for the same product. There were no substantial differences between flavors or between diet and regular soft drinks. The majority of soft drinks had fluoride levels exceeding 0.60 ppm. Variation in fluoride levels probably is due largely to the different water sources used in production. With no fluoride levels marked on the soft drink products or easily available from the manufacturers, it is not possible for clinicians or consumers to directly estimate fluoride ingestion from carbonated beverages. Therefore, to reduce the risk of dental fluorosis, dental and medical practitioners should be cautious about prescribing dietary fluoride supplements to preschool-aged children in nonfluoridated areas who consume large quantities of carbonated soft drinks.

SYSTEMIC FLUORIDE: Sources, Amounts, and Effects of Ingestion

Fluoride may be ingested from a variety of sources, including many foods and beverages. Fluoride intake varies greatly among individuals and is dependent on dietary constituents and use of fluoride products. Although ingestion of toxic amounts of fluoride is rare, the prevalence of dental fluorosis has increased in North America, suggesting that the levels of fluoride ingestion need to be closely monitored. Care should be taken to avoid excessive ingestion of fluoride dentifrice by preschoolaged children by placement of a small, pea-sized quantity on the toothbrush. Dietary fluoride supplements should be considered a targeted, preventive procedure only for those at elevated caries risk, and before prescribing them, careful consideration should be given to other fluoride sources, including home and child-care water supplies, foods, and beverages.

Proper use of fluoride products in fluoridated communities

The decision to add 1 mg fluoride per litre of water (or 1 ppm) was based on an extensive series of epidemiological surveys in communities with different concentrations of fluoride in their drinking water. These surveys had shown that in communities with fluoride at 1 ppm the prevalence of dental caries was 50‐65% lower than that in communities with only trace levels of fluoride. Only 10‐12% of children showed evidence of the mildest forms of dental fluorosis. 2 Dental fluorosis is a hypomineralisation of enamel of teeth caused by the chronic ingestion of excessive amounts of fluoride during the period when teeth are forming within the jaw. 3 Milder forms of dental fluorosis are characterised by whitish spots, striations, or diffuse opacities of teeth. Fluorosis does not affect the health of teeth or of an individual, but, in its more severe forms, may cause cosmetic concerns. Permanent teeth other than third molars are susceptible to the development of fluorosis in children aged up to 6 years. Excessive fluoride ingestion early in life tends to produce fluorosis in early forming and erupting permanent teeth, the incisors and first molars, whereas excessive ingestion in the later preschool years affects later forming and erupting permanent teeth, the canines, premolars, and second molars. In the 1950s and 1960s, several countries started to fluoridate their water. Hong Kong and Singapore fluoridated all their water supplies, and countries that provide fluoridated water to more than half their residents include Australia, Ireland, New Zealand, and the USA. Other countries with large water-fluoridation programmes include Brazil, Canada, Chile, and Malaysia. At the time fluoridation programmes began, fluoride that occurred naturally in drinking water and that which occurred naturally in some foods, primarily tea, seafood, and some grains, were essentially the only sources of ingested fluoride. Since then, several fluoride-containing products have been developed as alternatives to fluoridated water (dietary fluoride supplements) or as agents to provide fluoride topically to erupted teeth (fluoride toothpastes and mouth rinses and solutions, gels, and varnishes for professional application). About 20 years ago, investigators began to notice increased prevalences of dental fluorosis in school-aged children who were participants in epidemiological surveys or in clinical field trials in countries with established market economies. Most of the fluorosis observed was still mild, but there have been some increases as well in the intensity of fluorosis. Increases in the prevalence of fluorosis have been noted in non-fluoridated as well as fluoridated communities. 4 , 5

Patterns of dietary fluoride supplement use during infancy.

This paper reports on patterns of dietary fluoride supplement use during infancy. Data were collected by mail for a birth cohort (n = 1,072) studied at 6 weeks and 3, 6, 9, and 12 months of age. Percentages using supplements were 13.7 at 6 weeks, 13.4 at 3 months, 16.5 at 6 months, 13.0 at 9 months, and 12.1 at 12 months. Among those receiving supplements, mean proportions of weeks that supplements were received during the different time periods varied from 0.59 to 0.80. Number of days per week receiving supplements averaged 4.8 to 5.0. Mean fluoride dosages when supplements were received were 0.22 mg to 0.24 mg. Estimated average daily fluoride ingestion per day (among those receiving supplements during that time period and factoring in those days and weeks that supplements were not received) was 0.11 mg at 6 weeks, 0.15 mg at 3 months, 0.12 mg at 6 months, 0.11 mg at 9 months, and 0.14 mg at 12 months. Among the subset of 129 children with complete data at all time points who used supplements sometime during their first year of life, mean annual daily supplement dosage was 0.07 mg fluoride, with 75 percent having less than or equal to 0.10 mg. Those infants with mothers and fathers with more education were more likely to receive supplements. Group average use of fluoride supplements was fairly consistent over the 12 months; however, individual patterns varied substantially. Estimated actual mean daily fluoride intake when including days that supplements were not received was substantially less than the recommended 0.25 mg per day.

Fluoride loading of a lepidopteran larva ( Pieris brassicae) fed on treated diets

Experiments to assess the impact of dietary fluoride on larvae of Pieris brassicae were designed to substantiate field observations that at polluted sites little fluoride is absorbed by insect larvae and that most of the body load is caused by surface contamination. Treatment with fluoride as HF or AlF 3 had no effect on pupal weight of Pieris and we conclude that fluoride, at concentrations likely to be found on vegetation at polluted sites, is unlikely to have a direct impact on the growth of chewing herbivores. Fluoride in the gut formed the biggest component of the total body load. A significant amount of fluoride was detected in exuviae, but resulted from surface contamination. When larvae from polluted food were transferred to untreated food it took several days for the fluoride content of the faeces to return to background levels.

Brick tea consumption as the cause of dental fluorosis among children from Mongol, Kazak and Yugu populations in China

Dietary fluoride intake and the prevalence of dental fluorosis were investigated in children from three population groups (Mongol, Kazak and Yugu) in Gansu Province, China. The concentration of fluoride in drinking water ranged from 0.11 to 0.32 mg/litre; there was no other fluoride pollution. There was a high prevalence of dental fluorosis—52, 84 and 76% among the Mongol, Kazak and Yugu children, respectively). Dental fluorosis was particularly severe among the Kazak population (severity index: 2.00, 3.05 and 2.57 among the three populations, respectively). Each of the population groups had a long tradition of drinking milk tea made from brick tea water. This milk tea was found to contain high concentrations of fluoride (2.58–3.69 mg/litre). The daily fluorine consumption was 1.36–2.42-times the US RDA of 2.5 mg for children. Regression analysis showed that fluorosis was significantly correlated with the consumption of milk tea made from brick tea water, but not with any other dietary component (including milk).

Fluoride-induced lesions in the teeth of the short-tailed field vole (Microtus agrestis): a description of the dental pathology.

The effect of fluoride on the appearance of the teeth of the short-tailed field vole, Microtus agrestis, was investigated in both wild animals collected from field sites affected by different levels of industrial fluoride contamination and laboratory-reared animals consuming experimental grass diets of known fluoride concentration or with known fluoride concentrations in drinking water. The extent and severity of lesions on the surface and structure of both incisors and molars are described as six lesion types and related to the amount of biologically available orally ingested fluoride. In the incisors of voles consuming relatively low fluoride diets, lesions are mainly confined to those resulting from disruption of enamel pigmentation expressing itself as concentric bands of pigmentation-free areas on incisor surfaces. The visible effects on molars at low fluoride levels are confined to minor alterations in surface appearance. At higher levels of available dietary fluoride, effects on enamel pigmentation are superseded by alterations in the formation, composition, and strength of both enamel and dentine. The incisors exhibit a marked to severe increase in the cutting tip erosion rates with comparable increases in the extent of abnormal surface changes (enamel hypoplasia) and the loss of enamel pigmentation. The grinding surfaces of molars from animals exposed to high levels of dietary fluoride exhibit increasingly severe erosion of outer enamel regions, combined with cavitation and staining of the exposed central dentine. The mechanisms through which fluoride elicits increasingly visible and pathological alterations to the surface and subsurfaces of rodent teeth are discussed.

Fluoride‐induced lesions in the teeth of the short‐tailed field vole (Microtus agrestis): A description of the dental pathology

The effect of fluoride on the appearance of the teeth of the short-tailed field vole. Microtus agrestis, was investigated in both wild animals collected from field sites affected by different levels of industrial fluoride contamination and laboratory-reared animals consuming experimental grass diets of known fluoride concentration or with known fluoride concentrations in drinking water. The extent and severity of lesions on the surface and structure of both incisors and molars are described as six lesion types and related to the amount of biologically available orally ingested fluoride. In the incisors of voles consuming relatively low fluoride diets, lesions are mainly confined to those resulting from disruption of enamel pigmentation expressing itself as concentric bands of pigmentation-free areas on incisor surfaces. The visible effects on molars at low fluoride levels are confined to minor alterations in surface appearance. At higher levels of available dietary fluoride, effects on enamel pigmentation are superseded by alterations in the formation, composition, and strength of both enamel and dentine. The incisors exhibit a marked to severe increase in the cutting tip erosion rates with comparable increases in the extent of abnormal surface changes (enamel hypoplasia) and loss of enamel pigmentation. The grinding surfaces of molars from animals exposed to high levels of dietary fluoride exhibit increasingly severe erosion of outer enamel regions, combined with cavitation and staining of the exposed central dentine. The mechanisms through which fluoride elicits increasingly visible and pathological alterations to the surface and subsurfaces of rodent teeth are discussed. J Morphol 232: 155–167, 1997. © 1997 Wiley-Liss, Inc.

Effects of dietary fluoride and magnesium supplements on cyclic adenosine monophosphate (cAMP), calcium and magnesium levels in aorta of genetically hypercholesterolaemic RICO rats

Previous observations have suggested that low intakes of fluoride prevent pathological calcifications of internal organs, including the aortic wall, in experimental animals, fed a basically low magnesium diet. Our group found recently that fluoride has some potentially preventive effect against atherosclerotic serum lipid profiles in genetically hypercholesterolaemic rats. To study whether the apparently positive potential of fluoride against atherosclerosis is also reflected in aortic tissue, through its well known activation of adenylate cyclase, the aortic cAMP content of the rats used in our recent study was determined. Out of a total of 56 male RICO rats, mean weight 160 g, the control group C was fed an adequate diet, with 44% sucrose, a magnesium content of 883 p.p.m. and with 0.5% cholesterol. Group D had the same diet as group C except that the magnesium content was reduced to 200 p.p.m. Group E had the same diet as group D but with the fluoride content elevated from 1.9 to 12 p.p.m. Group G had the same diet as group E but with the magnesium content elevated from 200 to 300 p.p.m. After a feeding period of 6 weeks, the aortas of the animals were removed, cleaned and kept at -70°C until analysed. The mean cAMP content of the aortas, measured by radioimmunoassay, in groups C, D, E and G was 439, 546, 681, and 1394 μmol mg-1 protein, respectively. In group G only, the cAMP content was significantly higher than that of the other groups (p<0.001). The mean calcium and magnesium contents of the aortas of different groups did not significantly differ from each other. Thus in RICO rats, fed a high-sugar low-magnesium diet with cholesterol, supplementation of the diet with a small amount of fluoride elevates the cAMP content of the aorta, provided that the intake of Mg is not very low.

Infants' fluoride ingestion from water, supplements and dentifrice

Concerns about dental fluorosis and the paucity of detailed fluoride intake data prompted this longitudinal study of fluoride intake in infants from birth to 9 months of age. On average, water fluoride intake greatly exceeded that from dietary fluoride supplements or fluoride dentifrice. However, fluoride supplements and dentifrice contributed substantial proportions of fluoride intake among children using them. Some children had estimated fluoride intake from water, supplements and dentifrice that exceeded the recommended "optimal" intake (a level that has yet to be determined scientifically). Practitioners should estimate fluoride ingestion from all these sources if considering systemic fluoride supplementation.

Refining the estimate of the critical period for susceptibility to enamel fluorosis in human maxillary central incisors.

The purpose of this study was to determine an improved estimate of the critical period for susceptibility to fluorosis in human maxillary central incisors. The fluorosis score, S, of the incisal (I), middle (M), and cervical (C) third divisions on the labial surface of right maxillary central incisors of subjects (a representative sample of 1,085 Hong Kong Chinese children aged 7 to 12 years surveyed in 1986) was determined according to the Chronological Fluorosis Assessment (CFA) Index. Subject data were grouped by month of birth relative to June 1978, when the designated concentration for waterborne fluoride in the community water supply was reduced from 1.0 to 0.7 mg/L. The analytical task was one of finding the correlation maximum in a system of 12 variates and adjustable parameters including the waterborne fluoride concentration, [F-], and the fluorosis score. The main findings were: (1) the peak correlation of S vs [F-] for the male incisal third centered at 17.5 months after birth; (2) and six months later for females; (3) the correlation of S with [F-] is maximized for S(M) following S(I) by two months, and S(C) following S(M) by a further two months for both males and females; and (4) the critical period for exposure to fluoride is of about four months' duration for each third. The maxillary central incisor, as a whole, appears most at risk to fluorosis from dietary fluoride between age 15 and 24 months for males and between 21 and 30 months for females.

Infants' Fluoride Intake from Drinking Water Alone, and from Water Added to Formula, Beverages, and Food

In infants, the majority of total ingested fluoride is obtained from water, formula and beverages prepared with water, baby foods, and dietary fluoride supplements. Few studies have investigated the distribution of fluoride intake from these sources among young children at risk for dental fluorosis. The purpose of this study was to assess estimated water fluoride intake from different sources of water among a birth cohort studied longitudinally from birth until age 9 months. Parental reports were collected at 6 weeks, 3 months, 6 months, and 9 months of age for water, formula, beverage, and other dietary intake during the preceding week. Fluoride levels of home and child-care tap and bottled water sources were determined. This report estimates daily quantities of fluoride ingested only from water--both by itself and used to reconstitute formula, beverages, and food. Daily fluoride intake from water by itself ranged to 0.43 mg, with mean intakes < 0.05 mg. Water fluoride intake from reconstitution of concentrated infant formula ranged to 1.57 mg, with mean intakes by age from 0.18 to 0.31 mg. Fluoride intake from water added to juices and other beverages ranged to 0.67 mg, with means < 0.05 mg. Estimated total daily water fluoride intake ranged to 1.73 mg fluoride, with means from 0.29 to 0.38 mg.

Fluoride Supplementation for Children: Interim Policy Recommendations

The Committee on Nutrition of the American Academy of Pediatrics (AAP) last issued a statement in 1986 on the topic of fluoride supplementation for children. The recommendations made at that time recently have been reassessed because of what seems to be an increased incidence of dental fluorosis in children living in the United States. Dental fluorosis appears during tooth formation and is caused by excessive fluoride ingestion, which leads to enamel protein retention, hypomineralization of the dental enamel and dentin, and disruption of crystal formation. The effect is cosmetic only, ranging from barely perceptible white striations or specks to confluent areas of pitting or brownish gray staining. Teeth affected by fluorosis seem to continue to be resistant to dental caries. The main sources of fluoride include fluoridated water, foods or drinks reconstituted or prepared with fluoridated water, dentifrices, and fluoride supplements. Water is not fluoridated to a uniform level throughout the United States, and young children ingest significant but variable amounts of fluoride while brushing their teeth with fluoride-containing toothpaste. Because both of these sources of fluoride are difficult to control, attention has been directed again at the dosage of fluoride supplements to attempt to prevent dental fluorosis. In January 1994, a Dietary Fluoride Workshop sponsored by the American Dental Association was convened to address the issue of dental fluorosis. Although children can receive substantial amounts of fluoride from beverages and dentifrices, the experts at this workshop thought the only source of fluoride that could be easily altered was the supplement prescribed by physicians and dentists.

Commentary on and Recommendations for the Proper Uses of Fluoride

Fluorosis has been associated with the fluoride concentration of drinking water, use of dietary fluoride supplements, early use of dentifrices, and prolonged use of infant formula. The literature, however, does not show associations between fluorosis and use of fluoride mouthrinses, professionally applied fluorides, bottled waters, carbonated beverages, and juices. It is unwise to issue laundry lists of items that may be implicated as problem-causing when, in fact, they may not be. Although usually classified without fluorosis, children in Dean's "questionable" category would be classified with the condition if the TFI or TSIF were used. Accordingly, Dean, in 1942, really reported only 52.8 percent of children without fluorosis in Kewanee, a community with 0.9 ppm fluoride in drinking water. Because the morbidity and sequelae of dental caries have declined, undue emphasis has been placed recently on the risks of using fluoride rather than on its profound beneficial effects. Although of paramount importance, conclusions cannot be drawn on whether fluoride protects against, contributes to, or has no effect on bone fractures or is valuable in treating osteoporosis. Careful thought is required before making recommendations that may reduce health benefits because of unfounded concerns about perceived risks. There should be greater regulation of extraneous fluoride sources, rather than reliance on educational efforts or recommendations to eliminate use of highly effective preventive regimens.

Sources of Fluoride Intake in Children

Wide variations in fluoride intake among children make estimating fluoride intake difficult. This paper discusses the various sources of fluoride intake among children, beginning with a review of the fluoride concentrations of water and other beverages, foods, and therapeutic fluoride products. A review of previous studies' estimates of fluoride intake from diet, dentifrice, fluoride supplements, fluoride mouthrinses, and gels, as well as total fluoride intake also is presented. Then, estimates of fluoride intake among young children of different age groups are summarized, and examples demonstrating the high level of variability of fluoride intake, both from individual sources and in total, are presented. Lastly, this paper discusses the implications of our current level of knowledge of children's fluoride intake, and presents recommendations for the use of fluoride for children in light of this current knowledge. The major recommendations are that: (1) the fluoride content of foods and beverages, particularly infant formulas and water used in their reconstitution, should continue to be monitored closely in an effort to limit excessive fluoride intake; (2) ingestion of fluoride from dentifrice by young children should be controlled, and the use of only small quantities of dentifrice by young children should be emphasized; and (3) dietary fluoride supplements should be considered a targeted preventive regimen only for those children at higher risk for dental caries and with low levels of ingested fluoride from other sources.

How should we use dietary fluoride supplements?

Since January 1993 general dental practitioners have been able to prescribe dietary fluoride supplements in the form of drops or tablets for their child patients within the conditions of service of the General Dental Service. Many GDPs may already have taken advantage of this to the benefit of their patients. However, in recent years more evidence has become available about the impact of such fluoride supplements on the teeth.

Review of fluoride exposures and ingestion.

The literature on fluoride intake/ingestion was reviewed critically to determine the current exposure to fluorides for children living in non-fluoridated and fluoridated areas in North America. Fluoride from all sources except mouthrinses and professionally applied topical fluorides was considered, including ingestion from foods and beverages, as well as intake from the use of fluoride dentifrice and dietary fluoride supplements. Data from all of these sources were used to produce estimates of mean daily ingestion. Studies consistently have identified substantial variation in ingestion among individuals. These analyses demonstrated that a substantial proportion of individuals had exposure or ingestion well beyond that of the mean for each source, and often 10-20% received up to several times as much exposure as the mean. Some children probably ingest sufficient fluoride from a single source to exceed the "optimal" fluoride intake recommended from all sources, and are therefore at increased risk of fluorosis. This review highlighted the substantial variation and complexity of fluoride ingestion. Appropriate consideration of these aspects is warranted in efforts to ensure a margin of safety favoring dental caries prevention while limiting objectionable fluorosis.

Effects of plasma fluoride and dietary calcium concentrations on GI absorption and secretion of fluoride in the rat.

This 30-day balance study with weanling rats was designed to determine the effects of plasma fluoride and dietary calcium concentration and their interaction on the absorption, balance, and tissue concentrations of fluoride. The three major groups differed according to the total exposure and plasma concentrations of fluoride. One group received fluoride only in the diet and the other two received additional fluoride by continuous infusion from miniosmotic pumps implanted S.C. Each group was divided into two subgroups with dietary calcium concentrations of 0.4% or 1.4%. Fluoride intake with the diet did not differ among the groups. Fecal fluoride excretion was directly related to plasma fluoride concentration. The absorption and balance of dietary fluoride were inversely related to plasma fluoride concentration. These effects were greatest in the groups fed the 1.4% calcium diet. The interactions of plasma fluoride and dietary calcium on these variables were highly significant (P < 0.0001). The balance of dietary fluoride was negative in the four groups that received additional fluoride by infusion. In the two groups that received fluoride only in the diet, the plasma and bone fluoride concentrations were 41% and 59% lower, respectively, in the 1.4% dietary calcium group. The findings indicate that net fluoride secretion into the GI tract can occur when plasma fluoride concentrations and calcium intake are elevated. They suggest that elevated plasma fluoride levels and calcium intake are factors that may diminish the effect of oral fluoride treatment in osteoporotic patients.