Fluoride

After completing this article, readers should be able to: Widespread availability of fluoride is largely acknowledged as the major factor responsible for the declining prevalence of dental caries in the United States over the last 30 years. The impact of fluoride on teeth was studied initially in the early 1900s, when researchers noted that residents from communities in which there were naturally high fluoride levels in water seemed more resistant to dental decay. This observation led to the landmark investigation in the early 1940s of 21 cities that had varying levels of naturally occurring fluoride in the water. Results from this study identified 1 ppm (1 part per million or 1 mg/L) of fluoride in the water supply as the concentration that allowed for maximal caries prevention with minimal risk of fluorosis. Prospective field trials of water fluoridation in four pairs of treatment and control cities in the United States and Canada, begun in 1945, resulted in a 50% to 75% reduction in caries in children in the fluoridated communities during sequential cross-sectional surveys over 15 years.Since recognition of the association between fluoride and reduced risk of dental caries, the sources of fluoride in the diet have expanded substantially, and understanding of fluoride’s effects has evolved. This article reviews current understanding of fluoride’s mechanism of action, sources of fluoride in the diet, and the benefits and risks of fluoride, with the goal of enabling pediatricians to make well-informed decisions and provide appropriate advice about fluoride to families.Dental caries results from bacterial action on teeth. Bacteria coat the teeth in the form of plaque. Certain oral bacteria, primarily mutans streptococci, produce acid as the end product of carbohydrate metabolism. These acids dissolve the calcium-phosphate mineral of the tooth enamel or of the dentin. If not reversed or halted, this process results in formation of a carious lesion.Fluoride is an important defense against dental caries and can reverse or arrest early lesions. Fluoride inhibits caries by three mechanisms: enhancement of tooth mineralization, reversal of tooth demineralization, and inhibition of acid-producing bacteria responsible for caries. Demineralization and remineralization of the enamel is a dynamic process. Remineralization is enhanced and demineralization is inhibited when low levels of fluoride are sustained in the saliva and concentrated in the plaque. When present, fluoride aids in the incorporation of calcium and phosphate ions into the enamel and is itself incorporated in the mineralization process. Fluoride-containing enamel, fluoroapatite, is harder and less acid soluble than the original enamel that it replaces. In addition, fluoride has a direct inhibitory effect on bacterial acid production in vitro, thereby possibly limiting the underlying cause of the dental decay process.Early fluoride researchers believed that fluoride achieved its decay inhibitory effects through incorporation into teeth mineral prior to eruption, so-called pre-eruptive effects. Under this assumption, fluoride was only beneficial for young children. Although fluoride does provide some pre-eruptive protection against caries, in vitro, clinical, and epidemiologic evidence suggests the effects to be primarily posteruptive. Posteruptive effects mean that fluoride promotes reversal of early demineralization and cavitation of the teeth after they are erupted. Implications of fluoride’s posteruptive mechanism of action are twofold: Fluoride continues to have beneficial effects throughout the lifespan, and topical fluoride is effective and may have fewer systemic adverse effects than oral supplements.Fluoride is found in small amounts in almost all soil, water supplies, plants, and animals and, thus, is a normal constituent of all diets.Community water fluoridation provides both a topical and systemic source of fluoride. Regular consumption of fluoridated water provides sufficient topical exposure to fluoride to tip the caries balance (Fig. 1) in the direction of remineralization, provided the counteracting forces (eg, high bacterial load or impaired salivary flow) are not too great. According to a Centers for Disease Control and Prevention (CDC) fluoridation census in 2000, community water fluoridation is provided to 162 million Americans (about 57% of the population). Of these, about 10 million individuals are supplied by naturally fluoridated water. The United States Environmental Protection Agency (EPA) oversees regulations for drinking water provided by public water systems, including the maximum allowable fluoride concentration in naturally fluoridated water supplies. Under the Safe Drinking Water Act, the naturally occurring fluoride levels in community water supplies are not allowed to exceed 4 ppm, and water suppliers are required to notify consumers if the fluoride concentration of the water exceeds 2 ppm. Residents living in areas in which water supplies contain greater than 2 ppm of fluoride should seek an alternative source of water for children younger than 8 years of age to decrease the risk of enamel fluorosis. (1)Decisions to fluoridate community water supplies are made by state or local authorities. Most fluoridated drinking water has fluoride added to attain what is considered the optimal fluoride concentration of 0.7 to 1.2 ppm. The fluoride concentration of the water provided to communities depends on the average ambient temperatures; in warmer environments where water consumption is presumed to be higher, the lower end of the range is used. Most water supplies that do not have added fluoride contain less than 0.3 ppm, although some communities, particularly in the southwest and north central states, may have been supplied in the past by naturally fluoridated water containing 4 to 6 ppm. Well water contains variable amounts of fluoride, ranging from 0 to 7.22 ppm in one study. (2)Water filters and other point-of-use water treatment may affect the fluoride content of the water. Water treatments that potentially affect fluoride content of water include: activated charcoal filters, cellulose filters, reverse osmosis treatment, and distillation. Other water treatments, such as ultraviolet light exposure and water softeners, do not appreciably change the fluoride content of water. The processes of reverse osmosis and distillation remove virtually all fluoride from the water. Activated charcoal filters are the most common filtration devices in homes and may take the form of under-the-sink, faucet-mount, or pitcher-type units. We assessed the pitcher-type carbon filters and faucet-mounted filters of the two major manufacturers of water filters in the United States (Brita® [The Brita Products Co, Oakland, CA], Pur® [Proctor and Gamble, Cincinnati, OH]). Filtration through these units demonstrated a negligible effect on the fluoride concentration of tap water (Lewis and Castillo; unpublished data).Health professionals may assume that children drinking bottled water are receiving no fluoride and, therefore, need fluoride supplementation. A number of recent media reports have reinforced this concern with the public. However, bottled water contains variable amounts of fluoride, depending on the source and processing. Some bottled waters, particularly mineral waters, contain natural levels of fluoride comparable to or higher than optimally fluoridated community water. For example, Calistoga® (Nestlé Waters North America, Greenwich, CT) mineral water contains 0.9 ppm fluoride. (3) Nevertheless, most bottled waters contain minimal concentrations of fluoride. The United States Food and Drug Administration (FDA) does not require the labels of bottled water to list the fluoride concentration unless fluoride has been added. Approximately 20 of 900 brands of bottled water add fluoride to their product. The fluoridation in these products is adjusted according to the ambient temperature in the region where the water is sold, as specified by the FDA.Some foods, such as seafood and tea, are naturally high in fluoride. Many commercial beverages are prepared with water from areas of community water fluoridation and, therefore, are sources of fluoride. Examples include juices, juice drinks, and soda. As Americans consume more soda and juice in place of water and milk, these beverages that have “diffused” from fluoridated into nonfluoridated areas have become increasingly important sources of fluoride in the diet.The infant formula industry, in an effort to limit the fluoride concentration of their products, voluntarily reduced the fluoride content of formula in 1979. The reconstituted product now should reflect primarily the fluoride concentration of the water with which it is prepared; protein hydrosylate and soy-based formulas are somewhat higher in fluoride because the sources of calcium, added in preparation of the formulas, are appreciable sources of fluoride. Human milk contains only trace amounts of fluoride, even in the face of high maternal intakes or serum levels of fluoride.Fluoride toothpaste is a valuable delivery system for topical fluoride. After brushing with fluoride-containing toothpaste, fluoride levels in saliva peak, then remain at low concentrations for 2 to 6 hours, providing important anticaries effects. (4) Regular use of toothpaste, even in the absence of other sources of fluoride or dental care, can slow development of caries in young children at high risk for caries. A recent Cochrane Library systematic review of 74 studies of fluoride toothpaste concluded that “children aged 5 to 16 years who used a fluoridated toothpaste had fewer decayed, missing and filled permanent teeth … [regardless of whether their drinking water was fluoridated]. Twice a day use increases the benefit.” (5)In the United States, most toothpastes, including those marketed for children, contain approximately 1,100 ppm fluoride (1.1 mg/g toothpaste, 0.15% w/v, usually as 0.24% sodium fluoride or 0.76% sodium monofluorophosphate).As will be discussed later, young children swallow substantial amounts of toothpaste during toothbrushing. Swallowing fluoride toothpaste may provide a beneficial source of fluoride beyond its topical effect for children at high risk for caries (Table 1), but for children at low risk, early toothbrushing (ie, before 2 to 3 y of age) with fluoride paste may lead to an unacceptable risk of fluorosis. Because of fluorosis concerns, lower fluoride concentration toothpastes are available for young children in Europe, Australia, and New Zealand (but not the United States). Before the FDA could approve toothpaste with a lower fluoride level for children, a United States clinical trial would need to establish such a product’s efficacy in preventing caries. (1)Fluoride supplements, in the form of drops and tablets, were introduced in the late 1940s as an alternative source of fluoride for children living in nonfluoridated communities. The American Academy of Pediatrics (AAP) has published recommendations for fluoride supplementation based on water fluoride content and a child’s age (Table 2). Fluoride supplements are intended for children living in nonfluoridated areas to increase their fluoride exposure to levels similar to children living in optimally fluoridated areas. The most recent AAP guidelines, published in 1995, lowered the recommended fluoride supplement dose for children younger than 6 years of age and eliminated supplementation for infants younger than 6 months of age, in recognition of the risk of fluorosis with excess fluoride exposure during tooth development. Fluoride supplements are available in 0.25-, 0.5-, and 1.0-mg dosages. Many preparations combine fluoride with vitamins and iron. Fluoride supplement preparations in the United States are marketed in drop form for infants and young children and as chewable tablets and lozenges for older children (Table 3). Potential barriers to supplement use that must be considered are that a prescription is required to obtain fluoride and that the parents and child must be compliant with its administration.The effectiveness, risks, and benefits of fluoride supplements vary across the age range. In August 2001, the CDC Fluoride Recommendations Working Group released a report concluding that supplement use by pregnant women is not beneficial in preventing caries in the offspring. (1) The evidence that fluoride supplements prevent caries in children younger than age 6 years is mixed, with some studies reporting that supplements reduce the prevalence and severity of caries and others not showing such evidence. (1) The systematic review prepared for the current United States Preventive Task Force concluded that there was fair evidence that fluoride supplements prevented caries in children younger than 6 years of age. (6) The CDC found good evidence to support the use of fluoride supplements in children 6 years of age and older who are at high risk for caries. (1) In one clinical trial of supplement efficacy, investigators documented a 28% reduction in caries in schoolchildren who chewed, swished, and swallowed fluoride supplements compared with those who used placebo. (7)In addition to questions about the effectiveness of supplements in decreasing caries risk among young children, there is an increasing body of literature connecting fluoride supplements with a higher risk of fluorosis in young children. Because of concern for the association between fluoride supplements and enamel fluorosis, some countries recently revised their fluoride supplement recommendations. For example, in 2000, the Canadian Dental Association recommended limiting supplements to individuals at high risk for caries, starting supplements only after eruption of the first permanent teeth, and changing the dosing of supplements to a per body weight basis to allow for more precise fluoride intakes.The FDA approved fluoride mouthrinses as prescription anticaries agents in 1974. In 1980, a lower concentration (0.05% sodium fluoride or 230 ppm) fluoride mouthrinse was approved for OTC sales. A higher concentration formulation (0.2% sodium fluoride or 900 ppm) remains available by prescription and is recommended for use weekly or biweekly for at high risk for dental caries. Fluoride mouthrinses have been part of caries prevention A recent Cochrane systematic review concluded that use of fluoride mouthrinses reduced tooth decay in children, particularly in those who caries. younger than about years of age should not use fluoride mouthrinse because their control increases the of excess fluoride agents available for are fluoride and These products are recommended for individuals at high risk for caries. these concentrated fluoride products to the teeth a on the enamel that fluoride (1) This fluoride is available to areas of early decay. Because the of the it to it has been the product in the United or of fluoride has been with a to reduction in caries be used in young children because they swallow too is fluoride product that is to the United States, although it has been used in and as a caries prevention for more than 20 years. This concentrated ppm) product does not require preparation of the teeth, is with a small is to and can reverse early caries (Fig. 2). This a high concentration of fluoride against the teeth for hours, after which it (1) Fluoride has over in of use of and reduced that the child will swallow an A has that decrease caries in the permanent by Other studies have fluoride to be as effective as in preventing caries. A recent Cochrane systematic review concluded two to four a would reduce and tooth decay in However, the that is to the of caries reduction that can be to fluoride and to study and adverse effects. evidence that fluoride to fluorosis in young children has been (1) The FDA has approved fluoride as a for use as a before are and as a The FDA has not approved fluoride as an anticaries because this would require to United States clinical trial evidence of its However, based on their can use fluoride as an anticaries on an benefits of fluoride in decreasing caries have been documented review of studies documented that children who in fluoridated communities had 50% to fewer permanent teeth. The Task Force on Preventive concluded that fluoridated water reduced tooth decay by to 50% to what would be in those not fluoridated water. The decreasing over in caries levels between fluoridated and nonfluoridated communities has been to a availability of fluoride-containing toothpaste and other dental products and to the of fluoride-containing beverages into nonfluoridated areas. A recent both the direct and benefits of fluoridation concluded that its effectiveness remains decreasing caries risk by approximately among children years of age in the United Most studies have on the effect of fluoride among children, but it is now that exposure to fluoride and caries by about to among and the number of teeth that would have been to fluoridation is one of the public to be Prevention of dental caries, largely to fluoridation and fluoride-containing products, in dental in the United States from to In a recent the CDC that in communities of more than where it about per to fluoridate the in this in dental treatment community water fluoridation is an important of dental decay between lower and higher effects of exposure to excess fluoride take the form of dental and fluorosis. fluorosis, a is in the United only have been in the past years. results from exposure to high levels of fluoride during tooth in to the The adverse effects of dental fluorosis are primarily The effects of fluorosis range from across the tooth to more and of the (Fig. 3). that are with or fluorosis are more resistant to caries, but teeth in which fluorosis is may be more to decay because of the enamel of fluorosis is to the and dose of fluoride is of concern only in children younger than approximately 8 years of age, permanent teeth are After age 8 teeth no are to fluorosis. The risk of fluorosis during the late of permanent development. the because these teeth in where of fluoride is for fluorosis are most important for the permanent central of the The of to fluorosis for these teeth is to be between 15 and months for and 21 and 30 months of age for number of epidemiologic studies have that increase the risk of fluorosis, of which have fluoride supplements or early toothbrushing with fluoride toothpaste as two important risk A recent found that fluoride supplement use in nonfluoridated communities the risk of fluorosis at Other results have that sources of fluoride may increase the risk of fluorosis A risk of fluorosis of was when supplements fluoride toothpaste were used compared with with toothpaste children may be at greater risk for fluorosis because they more toothpaste when brushing their teeth. approximately two of the toothpaste used in to about one young children to after brushing may increase toothpaste Many young children do not have their teeth others may and than recommended Most recommendations for small children the In a and provided fluoride (Fig. young children teeth are a day with this of fluoride toothpaste potentially could consume the recommended of fluoride through toothbrushing fluoride (eg, from or fluoridated may to an risk of fluorosis. In children at low risk for caries, about fluorosis could take However, for children who are at high risk for caries, early toothbrushing with fluoride toothpaste provides a and beneficial source of topical of fluorosis, both in optimally fluoridated and nonfluoridated communities, to be increasing in the United In the only recent United States to about of children were to have some of fluorosis. This is compared with by in an optimally fluoridated community years However, most of fluorosis in the United States to be in the individuals can from consumption of optimally fluoridated water. toothpaste provides an source of concentrated fluoride that has important anticaries effects. However, the use of fluoridated toothpaste and other fluoride-containing treatments by young children should be considered only after a child’s risk for caries. risk is a and (1) to caries risk is in who have of the risk should be considered at high risk for caries and to such as use of and and providing sources of fluoride. For example, a child who has should be against or containing and may from the use of a fluoride-containing Certain are more to and more caries. Although not in these will caries, children in these to if they have risk and to for oral The of risk or early of caries the need for more (eg, early use of toothpaste, of fluoride For example, a child who has an older who required of dental caries is to from early of toothbrushing with a of fluoride-containing other to the fluoride These have had varying of in water fluoridation communities. the media that parents are to their over fluoride to their it is to the and by fluoride Some water fluoridation as and that fluoride should be a of A that fluoridation is a for example, to of their fluoride others from fluoride in the fluoride has been for number of including and Association between fluoride and these has not been by study. of that are to fluoride in literature are and A number of studies have the for an association between water fluoridation and these two but no evidence has been found to water fluoridation to an of exposure to fluoride from community water fluoride-containing and other sources has led to in caries in the United its years community water fluoridation has to be a and to prevent caries in individuals of all However, a increasing levels of fluorosis, it is that lower levels of fluoride in the water supply may be more appropriate is required to the optimal level of water fluoridation that will provide protection against risk for and soda contain variable amounts of fluoride. The of fluoridated beverages into nonfluoridated communities has to the decreasing in caries prevalence between communities with fluoridated and nonfluoridated water. it is to the fluoride content of beverages in the United States, which it for professionals to on fluoride and to the need for fluoride younger than 6 years of age should be allowed only a small of toothpaste per lower fluoride concentration toothpaste recommendations for toothpaste use in young children should be based on a child’s risk of caries. In children younger than years of age who are at low risk for caries should not use fluoride-containing toothpaste, although their teeth should be after with a or These risk of fluorosis from of toothpaste is greater than their risk of caries. For children in the age range who are at high risk of caries, prevention of caries should take over fluorosis A of fluoride toothpaste or with a or a provides an important source of fluoride for these fluoride supplements are available only by The AAP has published recommendations for fluoride supplementation based on water fluoride content and child’s age (Table 2). The CDC Fluoride Recommendations Group recently found evidence to fluoride supplement use for children younger than 6 years of age. In the topical fluoride (eg, fluoride may oral supplements as the recommended to provide sources of fluoride to children younger than age 6 years. evidence fluoride supplement use in children 6 years and older who are at high risk for caries. When fluoride supplements should be provided in or chewable to the topical

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