Water fluoridation
Encyclopedia
Water fluoridation is the controlled addition of fluoride
to a public water supply
to reduce tooth decay. Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride. Fluoridated water operates on tooth surfaces: in the mouth it creates low levels of fluoride in saliva
, which reduces the rate at which tooth enamel
demineralizes and increases the rate at which it remineralizes
in the early stages of cavities. Typically a fluoridated compound is added to drinking water, a process that in the U.S. costs an average of about $ per person-year. Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. A 1994 World Health Organization
expert committee suggested a level of fluoride from 0.5 to 1.0 mg/L (milligrams per litre), depending on climate. Bottled water
typically has unknown fluoride levels, and some domestic water filters remove some or all fluoride.
Dental caries
remain a major public health
concern in most industrialized countries, affecting 60–90% of schoolchildren and the vast majority of adults. Water fluoridation prevents cavities in both children and adults, with studies estimating an 18–40% reduction in cavities when water fluoridation is used by children who already have access to toothpaste and other sources of fluoride. Although water fluoridation can cause dental fluorosis
, which can alter the appearance of developing teeth
, most of this is mild and usually not considered to be of aesthetic or public-health concern. There is no clear evidence of other adverse effect
s. Moderate-quality studies have investigated effectiveness; studies on adverse effects have been mostly of low quality. Fluoride's effects depend on the total daily intake of fluoride from all sources. Drinking water is typically the largest source; other methods of fluoride therapy
include fluoridation of toothpaste, salt, and milk. Water fluoridation, when feasible and culturally acceptable, has substantial advantages, especially for subgroups at high risk. The U.S. Centers for Disease Control listed water fluoridation as one of the ten great public health achievements of the 20th century; in contrast, most European countries have experienced substantial declines in tooth decay without its use, primarily due to the introduction of fluoride toothpaste in the 1970s. The use of topical fluorides (such as in toothpaste) to prevent caries among people living in both industrialized and developing countries may help supplant the need for fluoridated water. Fluoridation may be more justified in the U.S. because of socioeconomic inequalities in dental health and dental care
. While water fluoridation is a predominantly American phenomenon, it has been introduced to many countries to varying degrees with many countries having water that is naturally fluoridated to recommended levels and others, such as in Europe, using fluoridated salts as an alternative source of fluoride.
The goal of water fluoridation is to prevent a chronic disease whose burdens particularly fall on children and on the poor. Its use presents a conflict between the common good
and individual rights
. It is controversial, and opposition to it has been based on ethical, legal, safety, and efficacy grounds. Health and dental organizations worldwide have endorsed its safety and effectiveness. Its use began in 1945, following studies of children in a region where higher levels of fluoride occur naturally in the water. Researchers discovered that moderate fluoridation prevents tooth decay, and as of 2004 about 400 million people worldwide received fluoridated water.
) is one of the most prevalent chronic diseases worldwide. Although it is rarely life-threatening, tooth decay can cause pain and impair eating, speaking, facial appearance, and acceptance into society, and it greatly affects the quality of life of children, particularly those of low socioeconomic status
. In most industrialized countries, tooth decay affects 60–90% of schoolchildren and the vast majority of adults; although the problem appears to be less in Africa's developing countries, it is expected to increase in several countries there because of changing diet and inadequate fluoride exposure. In the U.S., minorities and the poor both have higher rates of decayed and missing teeth, and their children have less dental care. Once a cavity occurs, the tooth's fate is that of repeated restorations, with estimates for the median life of an amalgam
tooth filling ranging from 9 to 14 years. Oral disease is the fourth most expensive disease to treat. The motivation for fluoridation of salt or water is similar to that of iodized salt for the prevention of mental retardation
and goiter.
These compounds were chosen for their solubility
, safety, availability, and low cost. A 1992 census found that, for U.S. public water supply systems reporting the type of compound used, 63% of the population received water fluoridated with fluorosilicic acid, 28% with sodium fluorosilicate, and 9% with sodium fluoride. The Centers for Disease Control and Prevention
has developed recommendations for water fluoridation that specify requirements for personnel, reporting, training, inspection, monitoring, surveillance, and actions in case of overfeed, along with technical requirements for each major compound used.
Although fluoride was once considered an essential nutrient
, the U.S. National Research Council has since removed this designation due to the lack of studies showing it is essential for human growth, though still considering fluoride a "beneficial element" due to its positive impact on oral health. The U.S. specifies the optimal level of fluoride to range from 0.7 to 1.2 mg/L (milligrams per liter, equivalent to parts per million), depending on the average maximum daily air temperature; the optimal level is lower in warmer climates, where people drink more water, and is higher in cooler climates. The U.S. standard, adopted in 1962, is not appropriate for all parts of the world and is based on assumptions that have become obsolete with the rise of air conditioning
and increased use of soft drinks, processed food, and other sources of fluorides. In 1994 a World Health Organization expert committee on fluoride use stated that 1.0 mg/L should be an absolute upper bound, even in cold climates, and that 0.5 mg/L may be an appropriate lower limit. A 2007 Australian systematic review recommended a range from 0.6 to 1.1 mg/L.
Fluoride in naturally occurring water can be above, at, or below recommended levels. Rivers and lakes generally contain fluoride levels less than 0.5 mg/L, but groundwater, particularly in volcanic or mountainous areas, can contain as much as 50 mg/L. Higher concentrations of fluorine
are found in alkaline volcanic
, hydrothermal, sedimentary, and other rocks
derived from highly evolved magma
s and hydrothermal solutions, and this fluorine dissolves
into nearby water as fluoride. In most drinking waters, over 95% of total fluoride is the F− ion
, with the magnesium
–fluoride complex
(MgF+) being the next most common. Because fluoride levels in water are usually controlled by the solubility of fluorite
(CaF2), high natural fluoride levels are associated with calcium
-deficient, alkaline, and soft waters. Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. It can be accomplished by percolating water through granular beds of activated alumina
, bone meal
, bone char
, or tricalcium phosphate
; by coagulation with alum
; or by precipitation
with lime
.
Pitcher
or faucet-mounted water filters do not alter fluoride; the more-expensive reverse osmosis
filters remove 65–95% of fluoride, and distillation
filters remove all fluoride. U.S. regulations for bottled water
do not require disclosing fluoride content, so the effect of always drinking it is not known. Surveys of bottled water in Cleveland and in Iowa found that most contained well below optimal fluoride levels; a survey in São Paulo, Brazil, found large variations of fluoride, with many bottles exceeding recommended limits and disagreeing with their labels.
, the key feature of which is an increase within dental plaque
of bacteria such as Streptococcus mutans
and Lactobacillus
. These produce organic acids when carbohydrates, especially sugar, are eaten. When enough acid is produced so that the pH
goes below 5.5, the acid dissolves carbonate
d hydroxyapatite, the main component of tooth enamel, in a process known as demineralization. After the sugar is gone, some of the mineral loss can be recovered—or remineralized
—from ions dissolved in the saliva. Cavities result when the rate of demineralization exceeds the rate of remineralization, typically in a process that requires many months or years.
All fluoridation methods, including water fluoridation, create low levels of fluoride ions in saliva and plaque fluid, thus exerting a topical
or surface effect. A person living in an area with fluoridated water may experience rises of fluoride concentration in saliva to about 0.04 mg/L several times during a day. Technically, this fluoride does not prevent cavities but rather controls the rate at which they develop. When fluoride ions are present in plaque fluid along with dissolved hydroxyapatite, and the pH is higher than 4.5, a fluorapatite
-like remineralized veneer
is formed over the remaining surface of the enamel; this veneer is much more acid-resistant than the original hydroxyapatite, and is formed more quickly than ordinary remineralized enamel would be. The cavity-prevention effect of fluoride is mostly due to these surface effects, which occur during and after tooth eruption
. Although some systemic (whole-body) fluoride returns to the saliva via blood plasma
, and to unerupted teeth via plasma or crypt fluid, there is little data to determine what percentages of fluoride's anticavity effect comes from these systemic mechanisms. Also, although fluoride affects the physiology of dental bacteria, its effect on bacterial growth
does not seem to be relevant to cavity prevention.
Fluoride's effects depend on the total daily intake of fluoride from all sources. About 70–90% of ingested fluoride is absorbed
into the blood, where it distributes throughout the body. In infants 80–90% of absorbed fluoride is retained, with the rest excreted, mostly via urine
; in adults about 60% is retained. About 99% of retained fluoride is stored in bone, teeth, and other calcium-rich areas, where excess quantities can cause fluorosis. Drinking water is typically the largest source of fluoride. In many industrialized countries swallowed toothpaste is the main source of fluoride exposure in unfluoridated communities. Other sources include dental products other than toothpaste; air pollution from fluoride-containing coal
or from phosphate fertilizers; trona
, used to tenderize meat in Tanzania
; and tea leaves, particularly the tea brick
s favored in parts of China. High fluoride levels have been found in other foods, including barley, cassava, corn, rice, taro, yams, and fish protein concentrate. The U.S. Institute of Medicine
has established Dietary Reference Intake
s for fluoride: Adequate Intake values range from 0.01 mg/day for infants aged 6 months or less, to 4 mg/day for men aged 19 years and up; and the Tolerable Upper Intake Level is 0.10 mg/kg/day for infants and children through age 8 years, and 10 mg/day thereafter. A rough estimate is that an adult in a temperate climate consumes 0.6 mg/day of fluoride without fluoridation, and 2 mg/day with fluoridation. However, these values differ greatly among the world's regions: for example, in Sichuan, China the average daily fluoride intake is only 0.1 mg/day in drinking water but 8.9 mg/day in food and 0.7 mg/day directly from the air due to the use of high-fluoride soft coal for cooking and drying foodstuffs indoors.
strongly suggests that water fluoridation reduces tooth decay. There is also consistent evidence that it causes dental fluorosis
, most of which is mild and not usually of aesthetic concern. There is no clear evidence of other adverse effects. Moderate-quality research exists as to water fluoridation's effectiveness and its potential association with cancer; research into other potential adverse effects has been almost all of low quality. Little high-quality research has been performed.
A 2000 systematic review
found that water fluoridation was statistically associated
with a decreased proportion of children with cavities (the median
of mean
decreases was 14.6%, the range
−5 to 64%), and with a decrease in decayed, missing
, and filled
primary teeth (the median of mean decreases was 2.25 teeth, the range 0.5–4.4 teeth), which is roughly equivalent to preventing 40% of cavities. The review found that the evidence was of moderate quality: many studies did not attempt to reduce observer bias, control for confounding factors, report variance measures, or use appropriate analysis. Although no major differences between natural and artificial fluoridation were apparent, the evidence was inadequate to reach a conclusion about any differences. Fluoride also prevents cavities in adults of all ages. There are fewer studies in adults however, and the design of water fluoridation studies in adults is inferior to that of studies of self- or clinically applied fluoride. A 2007 meta-analysis
found that water fluoridation prevented an estimated 27% of cavities in adults (95% confidence interval
[CI] 19–34%), about the same fraction as prevented by exposure to any delivery method of fluoride (29% average, 95% CI: 16–42%). A 2002 systematic review found strong evidence that water fluoridation is effective at reducing overall tooth decay in communities.
Most countries in Europe have experienced substantial declines in cavities without the use of water fluoridation. For example, in Finland and Germany, tooth decay rates remained stable or continued to decline after water fluoridation stopped. Fluoridation may be useful in the U.S. because unlike most European countries, the U.S. does not have school-based dental care, many children do not visit a dentist regularly, and for many U.S. children water fluoridation is the prime source of exposure to fluoride. The effectiveness of water fluoridation can vary according to circumstances such as whether preventive dental care is free.
Some studies suggest that fluoridation reduces oral health inequalities between the rich and poor
, but the evidence is limited. There is anecdotal but not scientific evidence that fluoride allows more time for dental treatment by slowing the progression of tooth decay, and that it simplifies treatment by causing most cavities to occur in pits and fissures of teeth.
Fluoride's adverse effects depend on total fluoride dosage from all sources. At the commonly recommended dosage, the only clear adverse effect is dental fluorosis
, which can alter the appearance of children's teeth during tooth development
; this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health. The critical period of exposure is between ages one and four years, with the risk ending around age eight. Fluorosis can be prevented by monitoring all sources of fluoride, with fluoridated water directly or indirectly responsible for an estimated 40% of risk and other sources, notably toothpaste, responsible for the remaining 60%. Compared to water naturally fluoridated at 0.4 mg/L, fluoridation to 1 mg/L is estimated to cause additional fluorosis in one of every 6 people (95% CI 4–21 people), and to cause additional fluorosis of aesthetic concern in one of every 22 people (95% CI 13.6–∞ people). Here, aesthetic concern is a term used in a standardized scale based on what adolescents would find unacceptable, as measured by a 1996 study of British 14-year-olds. In many industrialized countries the prevalence
of fluorosis is increasing even in unfluoridated communities, mostly because of fluoride from swallowed toothpaste. A 2009 systematic review indicated that fluorosis is associated with consumption of infant formula
or of water added to reconstitute the formula, that the evidence was distorted by publication bias
, and that the evidence that the formula's fluoride caused the fluorosis was weak. In the U.S. the decline in tooth decay was accompanied by increased fluorosis in both fluoridated and unfluoridated communities; accordingly, fluoride has been reduced in various ways worldwide in infant formulas, children's toothpaste, water, and fluoride-supplement schedules.
Fluoridation has little effect on risk of bone fracture
(broken bones); it may result in slightly lower fracture risk than either excessively high levels of fluoridation or no fluoridation. There is no clear association between fluoridation and cancer
or deaths due to cancer, both for cancer in general and also specifically for bone cancer and osteosarcoma
. Other adverse effects lack sufficient evidence to reach a confident conclusion. A Finnish study published in 1997 showed that fear that water is fluoridated may have a psychological effect with a large variety of symptoms, regardless of whether the water is actually fluoridated.
Fluoride can occur naturally in water in concentrations well above recommended levels, which can have several long-term adverse effects, including severe dental fluorosis, skeletal fluorosis
, and weakened bones. The World Health Organization recommends a guideline maximum fluoride value of 1.5 mg/L as a level at which fluorosis should be minimal.
In rare cases improper implementation of water fluoridation can result in overfluoridation that causes outbreaks of acute fluoride poisoning
, with symptoms that include nausea
, vomiting
, and diarrhea
. Three such outbreaks were reported in the U.S. between 1991 and 1998, caused by fluoride concentrations as high as 220 mg/L; in the 1992 Alaska outbreak, 262 people became ill and one person died. In 2010, approximately 60 gallons of fluoride were released into the water supply in Asheboro, North Carolina
in 90 minutes—an amount that was intended to be released in a 24-hour period.
Like other common water additives such as chlorine, hydrofluosilicic acid and sodium silicofluoride decrease pH and cause a small increase of corrosivity, but this problem is easily addressed by increasing the pH. Although it has been hypothesized that hydrofluosilicic acid and sodium silicofluoride might increase human lead
uptake from water, a 2006 statistical analysis did not support concerns that these chemicals cause higher blood lead concentrations in children. Trace levels of arsenic
and lead may be present in fluoride compounds added to water, but no credible evidence exists that their presence is of concern: concentration
s are below measurement limits.
The effect of water fluoridation on the natural environment has been investigated, and no adverse effects have been established. Issues studied have included fluoride concentrations in groundwater and downstream rivers; lawns, gardens, and plants; consumption of plants grown in fluoridated water; air emissions; and equipment noise.
, gel, and varnish
, and fluoridation of salt and milk. Dental sealant
s are effective as well, with estimates of prevented cavities ranging from 33% to 86%, depending on age of sealant and type of study.
Fluoride toothpaste
is the most widely used and rigorously evaluated fluoride treatment. Its introduction in the early 1970s is considered the main reason for the decline in tooth decay in industrialized countries, and toothpaste appears to be the single common factor in countries where tooth decay has declined. Toothpaste is the only realistic fluoride strategy in many low-income countries, where lack of infrastructure renders water or salt fluoridation infeasible. However, it relies on individual and family behavior, and its use is less likely among lower economic classes; in low-income countries it is unaffordable for the poor. Fluoride toothpaste prevents about 25% of cavities in young permanent teeth, and its effectiveness is improved if higher concentrations of fluoride are used, or if the toothbrushing is supervised. Fluoride mouthwash and gel are about as effective as fluoride toothpaste; fluoride varnish prevents about 45% of cavities. By comparison, brushing with a nonfluoride toothpaste has little effect on cavities.
The effectiveness of salt
fluoridation is about the same as that of water fluoridation, if most salt for human consumption is fluoridated. Fluoridated salt reaches the consumer in salt at home, in meals at school and at large kitchens, and in bread. For example, Jamaica has just one salt producer, but a complex public water supply; it started fluoridating all salt in 1987, achieving a notable decline in cavities. Universal salt fluoridation is also practiced in Colombia and the Swiss Canton of Vaud; in France and Germany fluoridated salt is widely used in households but unfluoridated salt is also available, giving consumers choice about fluoride. Concentrations of fluoride in salt range from 90 to 350 mg/kg, with studies suggesting an optimal concentration of around 250 mg/kg.
Milk
fluoridation is practiced by the Borrow Foundation in some parts of Bulgaria, Chile, Peru, Russia, Macedonia, Thailand and the UK. Depending on location, the fluoride is added to milk, to powdered milk
, or to yogurt. For example, milk-powder fluoridation is used in rural Chilean areas where water fluoridation is not technically feasible. These programs are aimed at children, and have neither targeted nor been evaluated for adults. A 2005 systematic review found insufficient evidence to support the practice, but also concluded that studies suggest that fluoridated milk benefits schoolchildren, especially their permanent teeth.
Other public-health strategies to control tooth decay, such as education to change behavior and diet, have lacked impressive results. Although fluoride is the only well-documented agent which controls the rate at which cavities develop, it has been suggested that adding calcium
to the water would reduce cavities further. Other agents to prevent tooth decay include antibacterials such as chlorhexidine and sugar substitutes such as xylitol
. Xylitol-sweetened chewing gum
has been recommended as a supplement to fluoride and other conventional treatments if the gum is not too costly. Two proposed approaches, bacteria replacement therapy (probiotics) and caries vaccine
, would share water fluoridation's advantage of requiring only minimal patient compliance, but have not been proven safe and effective. Other experimental approaches include fluoridated sugar, polyphenol
s, and casein phosphopeptide–amorphous calcium phosphate nanocomplexes
.
A 2007 Australian review concluded that water fluoridation is the most effective and socially the most equitable way to expose entire communities to fluoride's cavity-prevention effects. A 2002 U.S. review estimated that sealants decreased cavities by about 60% overall, compared to about 18–50% for fluoride. A 2007 Italian review suggested that water fluoridation may not be needed, particularly in the industrialized countries where cavities have become rare, and concluded that toothpaste and other topical fluoride offers a best way to prevent cavities worldwide. A 2004 World Health Organization review stated that water fluoridation, when it is culturally acceptable and technically feasible, has substantial advantages in preventing tooth decay, especially for subgroups at high risk.
or gel costs an estimated $ per person-year. Assuming the worst case, with the lowest estimated effectiveness and highest estimated operating costs for small cities, fluoridation costs an estimated $–$ per saved tooth-decay surface, which is lower than the estimated $ to restore the surface and the estimated $ average discounted
lifetime cost of the decayed surface, which includes the cost to maintain the restored tooth surface. It is not known how much is spent in industrial countries to treat dental fluorosis, which is mostly due to fluoride from swallowed toothpaste.
Although a 1989 workshop on cost-effectiveness
of cavity prevention concluded that water fluoridation is one of the few public health measures that save more money than they cost, little high-quality research has been done on the cost-effectiveness and solid data are scarce. Dental sealants are cost-effective only when applied to high-risk children and teeth. A 2002 U.S. review estimated that on average, sealing first permanent molars
saves costs when they are decaying faster than 0.47 surfaces per person-year whereas water fluoridation saves costs when total decay incidence
exceeds 0.06 surfaces per person-year. In the U.S., water fluoridation is more cost-effective than other methods to reduce tooth decay in children, and a 2008 review concluded that water fluoridation is the best tool for combating cavities in many countries, particularly among socially disadvantaged groups.
U.S. data from 1974–1992 indicate that when water fluoridation is introduced into a community, there are significant decreases in the number of employees per dental firm and the number of dental firms. The data suggest that some dentists respond to the demand shock
by moving to non-fluoridated areas and by retraining as specialists. U.S. children born 1957–1964 who grew up in fluoridated areas have earned significantly more as adults than children who did not; this effect is heavily concentrated among girls from poorer families, consistent with the hypothesis that the effect is due to consumer and employer discrimination in favor of women with physically more attractive
teeth.
and food fortification
, fluoridation presents a conflict between benefiting the common good and infringing on individual rights. Fluoridation can be viewed as a violation of ethical
or legal rules that prohibit medical treatment without medical supervision or informed consent, and that prohibit administration of unlicensed medical substances. It can also be viewed as a public intervention to replicate the benefits of naturally fluoridated water in order to free people from the misery of toothache
and dental work, with greatest benefit to those least able to help themselves, and where it would be unethical to withhold such treatment.
National and international health agencies and dental associations throughout the world have endorsed water fluoridation's safety and effectiveness. The Centers for Disease Control and Prevention listed water fluoridation as one of the ten great public health achievements of the 20th century, alongside vaccination
, family planning
, recognition of the dangers of smoking, and other achievements. Other organizations endorsing fluoridation include the World Health Organization, the U.S. Surgeon General, the American Public Health Association
, the European Academy of Paediatric Dentistry, and the national dental associations of Australia, Canada, and the U.S.
Despite support by public health organizations and authorities, efforts to introduce water fluoridation have met considerable opposition, opposition that is "often based on Internet resources or published books that present a highly misleading picture of water fluoridation". Since fluoridation's inception, proponents have argued for scientific optimism and faith in experts, while opponents have drawn on distrust of experts and unease about medicine and science. Controversies include disputes over fluoridation's benefits and the strength of the evidence basis for these benefits, the difficulty of identifying harms, legal issues over whether water fluoridation is a medicine, and the ethics of mass intervention. U.S. opponents of fluoridation were heartened by a 2006 National Research Council
report about hazards of water naturally fluoridated to high levels; the report recommended lowering the U.S. maximum limit of 4 mg/L for fluoride in drinking water. Opposition campaigns involve newspaper articles, talk radio, and public forums. Media reporters are often poorly equipped to explain the scientific issues, and are motivated to present controversy regardless of the underlying scientific merits. Internet websites, which are increasingly used by the public for health information, contain a wide range of material about fluoridation ranging from factual to fraudulent, with a disproportionate percentage opposed to fluoridation. Antifluoridationist literature links fluoride exposure to a wide variety of effects, including AIDS
, allergy
, Alzheimer's, arthritis
, cancer
, and low IQ, along with diseases of the gastrointestinal tract
, kidney
, pineal gland
, and thyroid
.
Conspiracy theories involving fluoridation are common, and include claims that fluoridation was motivated by protecting the U.S. atomic bomb program from litigation, that (as famously parodied in the film Dr. Strangelove) it is part of a Communist or New World Order plot to take over the world, that it was pioneered by a German chemical company to make people submissive to those in power, that behind the scenes it is promoted by the sugary food or phosphate fertilizer or aluminum industries, or that it is a smokescreen to cover failure to provide dental care to the poor. One such theory is that fluoridation was a public-relations ruse sponsored by fluoride polluters such as the aluminum maker Alcoa
and the Manhattan Project
, with conspirators that included industrialist Andrew Mellon and the Mellon Institute's researcher Gerald J. Cox, the Kettering Laboratory of the University of Cincinnati
, the Federal Security Agency
's administrator Oscar R. Ewing, and public-relations strategist Edward Bernays
. Specific antifluoridation arguments change to match the spirit of the time.
Opponents of fluoridation include some researchers, dental and medical professionals, alternative medical practitioners such as chiropractors, and health food enthusiasts; a few religious objectors, mostly Christian Scientists in the U.S.; and occasionally consumer groups and environmentalists. Organized political opposition has come from right-wing groups such as the John Birch Society
, libertarians, and from left-wing groups like Green parties in the UK and New Zealand. Many people do not know that fluoridation is meant to prevent tooth decay, or that natural or bottled water can contain fluoride; as the general public does not have a particular view on fluoridation, the debate may reflect an argument between two relatively small lobbies
for and against fluoridation. A 2009 survey of Australians found that 70% supported and 15% opposed fluoridation; those opposed were much more likely to score higher on outrage factor
s such as "unclear benefits". A 2003 study of focus groups from 16 European countries found that fluoridation was opposed by a majority of focus group members in most of the countries, including France, Germany, and the UK. A 1999 survey in Sheffield
, UK found that while a 62% majority favored water fluoridation in the city, the 31% that were opposed expressed their preference
with greater intensity than supporters. A 2007 Scottish bioethics
council report concluded that good evidence for or against water fluoridation is lacking, therefore local and regional democratic procedures are the most appropriate way to decide whether to fluoridate. Every year in the U.S., pro- and anti-fluoridationists face off in referenda or other public decision-making processes: in most of them, fluoridation is rejected. In the U.S., rejection is more likely when the decision is made by a public referendum; in Europe, most decisions against fluoridation have been made administratively. Neither side of the dispute appears to be weakening or willing to concede.
Water fluoridation's science and practice are predominantly American. It has been introduced to varying degrees in many countries and territories outside the U.S., including Argentina, Australia, Brazil, Canada, Chile, Colombia, Hong Kong, Ireland, Israel, Korea, Malaysia, New Zealand, the Philippines, Singapore, Spain, the UK, and Vietnam. An estimated 12 million people in western Europe, 171 million in the U.S. (61.5% of the U.S. population), and 355 million worldwide receive artificially fluoridated water, in addition to at least 50 million worldwide who receive water naturally fluoridated to recommended levels.
In addition, at least 50 million people worldwide drink water that is naturally fluoridated to optimal levels; the actual number is unknown and is likely to be much higher. Naturally fluoridated water is used in many countries, including Argentina, France, Gabon, Libya, Mexico, Senegal, Sri Lanka, Tanzania, the U.S., and Zimbabwe. In some locations, notably parts of Africa, China, and India, natural fluoridation exceeds recommended levels; in China an estimated 200 million people receive water fluoridated at or above recommended levels.
Communities have discontinued water fluoridation in some countries, including Finland, Germany, Japan, the Netherlands, Sweden, and Switzerland. This change was often motivated by political opposition to water fluoridation, but sometimes the need for water fluoridation was met by alternative strategies. The use of fluoride in its various forms is the foundation of tooth decay prevention throughout Europe; for example, France, Germany, and many other European countries use fluoridated salt.
The relationship between fluoride and teeth has been studied since the early 19th century. By 1850, investigators had established that fluoride occurs with varying concentrations in teeth, bone, and drinking water. By 1900, they had speculated that fluoride would protect against tooth decay, proposed supplementing the diet with fluoride, and observed mottled tooth enamel (now called dental fluorosis) without knowing the cause.
The history of water fluoridation can be divided into three periods. The first was research into the cause of a form of mottled tooth enamel called the Colorado brown stain. The second (c. 1933–1945) focused on the relationship between fluoride concentrations, fluorosis, and tooth decay, and established that moderate levels of fluoride prevent cavities. The third period, from 1945 on, focused on adding fluoride to community water supplies.
The foundation of water fluoridation in the U.S. was the research of the dentist Frederick McKay. McKay spent thirty years investigating the cause of what was then known as the Colorado brown stain, which produced mottled but also cavity-free teeth; with the help of G.V. Black and other researchers, he established that the cause was fluoride. The first report of a statistical association between the stain and lack of tooth decay was made by UK dentist Norman Ainsworth in 1925. In 1931, an Alcoa
chemist, H.V. Churchill, concerned about a possible link between aluminum and staining, analyzed water from several areas where the staining was common and found that fluoride was the common factor.
In the 1930s and early 1940s, H. Trendley Dean and colleagues at the U.S. National Institutes of Health published several epidemiological studies suggesting that a fluoride concentration of about 1 mg/L was associated with substantially fewer cavities in temperate climates, and that it increased fluorosis but only to a level that was of no medical or aesthetic concern. Other studies found no other significant adverse effects even in areas with fluoride levels as high as 8 mg/L. To test the hypothesis that adding fluoride would prevent cavities, Dean and his colleagues conducted a controlled experiment by fluoridating the water in Grand Rapids, Michigan
, starting January 25, 1945. The results, published in 1950, showed significant reduction of cavities. Significant reductions in tooth decay were also reported by important early studies outside the U.S., including the Brantford–Sarnia–Stratford study in Canada (1945–1962), the Tiel–Culemborg study in the Netherlands (1953–1969), the Hastings study in New Zealand (1954–1970), and the Department of Health study in the U.K. (1955–1960). By present-day standards these and other pioneering studies were crude, but the large reductions in cavities convinced public health professionals of the benefits of fluoridation.
Fluoridation became an official policy of the U.S. Public Health Service by 1951, and by 1960 water fluoridation had become widely used in the U.S., reaching about 50 million people. By 2006, 69.2% of the U.S. population on public water systems were receiving fluoridated water, amounting to 61.5% of the total U.S. population; 3.0% of the population on public water systems were receiving naturally occurring fluoride. In some other countries the pattern was similar. New Zealand, which led the world in per-capita sugar consumption and had the world's worst teeth, began fluoridation in 1953, and by 1968 fluoridation was used by 65% of the population served by a piped water supply. Fluoridation was introduced into Brazil in 1953, was regulated by federal law starting in 1974, and by 2004 was used by 71% of the population. In the Republic of Ireland, fluoridation was legislated in 1960, and after a constitutional challenge the two major cities of Dublin and Cork began it in 1964; fluoridation became required for all sizeable public water systems and by 1996 reached 66% of the population. In other locations, fluoridation was used and then discontinued: in Kuopio
, Finland, fluoridation was used for decades but was discontinued because the school dental service provided significant fluoride programs and the cavity risk was low, and in Basle, Switzerland, it was replaced with fluoridated salt.
McKay's work had established that fluorosis occurred before tooth eruption
. Dean and his colleagues assumed that fluoride's protection against cavities was also pre-eruptive, and this incorrect assumption was accepted for years. By 2000, however, the topical effects of fluoride (in both water and toothpaste) were well understood, and it had become known that a constant low level of fluoride in the mouth works best to prevent cavities.
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
to a public water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...
to reduce tooth decay. Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride. Fluoridated water operates on tooth surfaces: in the mouth it creates low levels of fluoride in saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
, which reduces the rate at which tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
demineralizes and increases the rate at which it remineralizes
Remineralisation of teeth
Remineralisation of teeth is a process in which minerals are returned to the molecular structure of the tooth itself. Teeth are porous allowing fluids and demineralisation beneath the surface of the tooth. When demineralised, these pores become larger...
in the early stages of cavities. Typically a fluoridated compound is added to drinking water, a process that in the U.S. costs an average of about $ per person-year. Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. A 1994 World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
expert committee suggested a level of fluoride from 0.5 to 1.0 mg/L (milligrams per litre), depending on climate. Bottled water
Bottled water
Bottled water is drinking water packaged in plastic or glass water bottles. Bottled water may be carbonated or not...
typically has unknown fluoride levels, and some domestic water filters remove some or all fluoride.
Dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...
remain a major public health
Public health
Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals" . It is concerned with threats to health based on population health...
concern in most industrialized countries, affecting 60–90% of schoolchildren and the vast majority of adults. Water fluoridation prevents cavities in both children and adults, with studies estimating an 18–40% reduction in cavities when water fluoridation is used by children who already have access to toothpaste and other sources of fluoride. Although water fluoridation can cause dental fluorosis
Dental fluorosis
Dental fluorosis is a developmental disturbance of dental enamel caused by excessive exposure to high concentrations of fluoride during tooth development. The risk of fluoride overexposure occurs between the ages of 3 months and 8 years. In its mild forms , fluorosis often appears as unnoticeable,...
, which can alter the appearance of developing teeth
Tooth development
Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. Although many diverse species have teeth, non-human tooth development is largely the same as in humans...
, most of this is mild and usually not considered to be of aesthetic or public-health concern. There is no clear evidence of other adverse effect
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
s. Moderate-quality studies have investigated effectiveness; studies on adverse effects have been mostly of low quality. Fluoride's effects depend on the total daily intake of fluoride from all sources. Drinking water is typically the largest source; other methods of fluoride therapy
Fluoride therapy
Fluoride therapy is the delivery of fluoride to the teeth topically or systemically in order to prevent tooth decay which results in cavities. Most commonly, fluoride is applied topically to the teeth using gels, varnishes, toothpaste/dentifrices or mouth rinse. Systemic delivery involves...
include fluoridation of toothpaste, salt, and milk. Water fluoridation, when feasible and culturally acceptable, has substantial advantages, especially for subgroups at high risk. The U.S. Centers for Disease Control listed water fluoridation as one of the ten great public health achievements of the 20th century; in contrast, most European countries have experienced substantial declines in tooth decay without its use, primarily due to the introduction of fluoride toothpaste in the 1970s. The use of topical fluorides (such as in toothpaste) to prevent caries among people living in both industrialized and developing countries may help supplant the need for fluoridated water. Fluoridation may be more justified in the U.S. because of socioeconomic inequalities in dental health and dental care
Dentistry
Dentistry is the branch of medicine that is involved in the study, diagnosis, prevention, and treatment of diseases, disorders and conditions of the oral cavity, maxillofacial area and the adjacent and associated structures and their impact on the human body. Dentistry is widely considered...
. While water fluoridation is a predominantly American phenomenon, it has been introduced to many countries to varying degrees with many countries having water that is naturally fluoridated to recommended levels and others, such as in Europe, using fluoridated salts as an alternative source of fluoride.
The goal of water fluoridation is to prevent a chronic disease whose burdens particularly fall on children and on the poor. Its use presents a conflict between the common good
Common good
The common good is a term that can refer to several different concepts. In the popular meaning, the common good describes a specific "good" that is shared and beneficial for all members of a given community...
and individual rights
Individual rights
Group rights are rights held by a group rather than by its members separately, or rights held only by individuals within the specified group; in contrast, individual rights are rights held by individual people regardless of their group membership or lack thereof...
. It is controversial, and opposition to it has been based on ethical, legal, safety, and efficacy grounds. Health and dental organizations worldwide have endorsed its safety and effectiveness. Its use began in 1945, following studies of children in a region where higher levels of fluoride occur naturally in the water. Researchers discovered that moderate fluoridation prevents tooth decay, and as of 2004 about 400 million people worldwide received fluoridated water.
Goal
The goal of water fluoridation is to prevent tooth decay by adjusting the concentration of fluoride in public water supplies. Tooth decay (dental cariesDental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...
) is one of the most prevalent chronic diseases worldwide. Although it is rarely life-threatening, tooth decay can cause pain and impair eating, speaking, facial appearance, and acceptance into society, and it greatly affects the quality of life of children, particularly those of low socioeconomic status
Socioeconomic status
Socioeconomic status is an economic and sociological combined total measure of a person's work experience and of an individual's or family’s economic and social position in relation to others, based on income, education, and occupation...
. In most industrialized countries, tooth decay affects 60–90% of schoolchildren and the vast majority of adults; although the problem appears to be less in Africa's developing countries, it is expected to increase in several countries there because of changing diet and inadequate fluoride exposure. In the U.S., minorities and the poor both have higher rates of decayed and missing teeth, and their children have less dental care. Once a cavity occurs, the tooth's fate is that of repeated restorations, with estimates for the median life of an amalgam
Amalgam (dentistry)
Amalgam is an alloy containing mercury. The term is commonly used for the amalgam employed as material for dental fillings, which consists of mercury , silver , tin , copper , and other trace metals...
tooth filling ranging from 9 to 14 years. Oral disease is the fourth most expensive disease to treat. The motivation for fluoridation of salt or water is similar to that of iodized salt for the prevention of mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
and goiter.
Implementation
Fluoridation does not affect the appearance, taste, or smell of drinking water. It is normally accomplished by adding one of three compounds to the water: sodium fluoride, fluorosilicic acid, or sodium fluorosilicate.- Sodium fluorideSodium fluorideSodium fluoride is an inorganic chemical compound with the formula NaF. A colorless solid, it is a source of the fluoride ion in diverse applications. Sodium fluoride is less expensive and less hygroscopic than the related salt potassium fluoride....
(NaF) was the first compound used and is the reference standardReference standardA drug reference standard is a standardized substance which is used as a measurement base for similar substances. Where the exact active substances of a new drug are not known, a reference standard provides a calibrated level of biological effects against which new preparations of the drug can be...
. It is a white, odorless powder or crystal; the crystalline form is preferred if manual handling is used, as it minimizes dust. It is more expensive than the other compounds, but is easily handled and is usually used by smaller utility companies. - Fluorosilicic acid (H2SiF6) is an inexpensive liquid by-productBy-productA by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....
of phosphate fertilizer manufacture. It comes in varying strengths, typically 23–25%; because it contains so much water, shipping can be expensive. It is also known as hexafluorosilicic, hexafluosilicic, hydrofluosilicic, and silicofluoric acid. - Sodium fluorosilicate (Na2SiF6) is a powder or very fine crystal that is easier to ship than fluorosilicic acid. It is also known as sodium silicofluoride.
These compounds were chosen for their solubility
Solubility
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
, safety, availability, and low cost. A 1992 census found that, for U.S. public water supply systems reporting the type of compound used, 63% of the population received water fluoridated with fluorosilicic acid, 28% with sodium fluorosilicate, and 9% with sodium fluoride. The Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
has developed recommendations for water fluoridation that specify requirements for personnel, reporting, training, inspection, monitoring, surveillance, and actions in case of overfeed, along with technical requirements for each major compound used.
Although fluoride was once considered an essential nutrient
Essential nutrient
An essential nutrient is a nutrient required for normal body functioning that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health , and thus must be obtained from a dietary source...
, the U.S. National Research Council has since removed this designation due to the lack of studies showing it is essential for human growth, though still considering fluoride a "beneficial element" due to its positive impact on oral health. The U.S. specifies the optimal level of fluoride to range from 0.7 to 1.2 mg/L (milligrams per liter, equivalent to parts per million), depending on the average maximum daily air temperature; the optimal level is lower in warmer climates, where people drink more water, and is higher in cooler climates. The U.S. standard, adopted in 1962, is not appropriate for all parts of the world and is based on assumptions that have become obsolete with the rise of air conditioning
Air conditioning
An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
and increased use of soft drinks, processed food, and other sources of fluorides. In 1994 a World Health Organization expert committee on fluoride use stated that 1.0 mg/L should be an absolute upper bound, even in cold climates, and that 0.5 mg/L may be an appropriate lower limit. A 2007 Australian systematic review recommended a range from 0.6 to 1.1 mg/L.
Fluoride in naturally occurring water can be above, at, or below recommended levels. Rivers and lakes generally contain fluoride levels less than 0.5 mg/L, but groundwater, particularly in volcanic or mountainous areas, can contain as much as 50 mg/L. Higher concentrations of fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
are found in alkaline volcanic
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...
, hydrothermal, sedimentary, and other rocks
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
derived from highly evolved magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
s and hydrothermal solutions, and this fluorine dissolves
Solvation
Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...
into nearby water as fluoride. In most drinking waters, over 95% of total fluoride is the F− ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
, with the magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
–fluoride complex
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
(MgF+) being the next most common. Because fluoride levels in water are usually controlled by the solubility of fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
(CaF2), high natural fluoride levels are associated with calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
-deficient, alkaline, and soft waters. Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. It can be accomplished by percolating water through granular beds of activated alumina
Activated alumina
Activated alumina is manufactured from aluminium hydroxide by dehydroxylating it in a way that produces a highly porous material; this material can have a surface area significantly over 200 square metres/g. The compound is used as a desiccant and as a filter of fluoride, arsenic and selenium in...
, bone meal
Bone meal
Bone meal is a mixture of crushed and coarsely ground bones that is used as an organic fertilizer for plants and formerly in animal feed. As a slow-release fertilizer, bone meal is primarily used as a source of phosphorus....
, bone char
Bone char
Bone char, also known as bone black, ivory black, animal charcoal, or abaiser, is a granular material produced by charring animal bones. To prevent the spread of mad-cow disease, the skull and spine are never used...
, or tricalcium phosphate
Tricalcium phosphate
Tricalcium phosphate is a calcium salt of phosphoric acid with the chemical formula Ca32. It is also known as tribasic calcium phosphate or "bone ash" ....
; by coagulation with alum
Alum
Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...
; or by precipitation
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
with lime
Lime (mineral)
Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely...
.
Pitcher
Pitcher (container)
A pitcher is a container with a spout used for storing and pouring contents which are liquid in form. Generally a pitcher also has a handle, which makes pouring easier.A ewer is a vase-shaped pitcher, often decorated, with a base and a flaring spout...
or faucet-mounted water filters do not alter fluoride; the more-expensive reverse osmosis
Reverse osmosis
Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...
filters remove 65–95% of fluoride, and distillation
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
filters remove all fluoride. U.S. regulations for bottled water
Bottled water
Bottled water is drinking water packaged in plastic or glass water bottles. Bottled water may be carbonated or not...
do not require disclosing fluoride content, so the effect of always drinking it is not known. Surveys of bottled water in Cleveland and in Iowa found that most contained well below optimal fluoride levels; a survey in São Paulo, Brazil, found large variations of fluoride, with many bottles exceeding recommended limits and disagreeing with their labels.
Mechanism
Fluoride exerts its major effect by interfering with the demineralization mechanism of tooth decay. Tooth decay is an infectious diseaseInfectious disease
Infectious diseases, also known as communicable diseases, contagious diseases or transmissible diseases comprise clinically evident illness resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism...
, the key feature of which is an increase within dental plaque
Dental plaque
Dental plaque is a biofilm, usually a pale yellow, that develops naturally on the teeth. Like any biofilm, dental plaque is formed by colonizing bacteria trying to attach themselves to a smooth surface...
of bacteria such as Streptococcus mutans
Streptococcus mutans
Streptococcus mutans is a facultatively aerobic, Gram-positive coccus-shaped bacterium commonly found in the human oral cavity and is a significant contributor to tooth decay.The microbe was first described by J Kilian Clarke in 1924.-Introduction:...
and Lactobacillus
Lactobacillus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...
. These produce organic acids when carbohydrates, especially sugar, are eaten. When enough acid is produced so that the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
goes below 5.5, the acid dissolves carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
d hydroxyapatite, the main component of tooth enamel, in a process known as demineralization. After the sugar is gone, some of the mineral loss can be recovered—or remineralized
Remineralisation of teeth
Remineralisation of teeth is a process in which minerals are returned to the molecular structure of the tooth itself. Teeth are porous allowing fluids and demineralisation beneath the surface of the tooth. When demineralised, these pores become larger...
—from ions dissolved in the saliva. Cavities result when the rate of demineralization exceeds the rate of remineralization, typically in a process that requires many months or years.
All fluoridation methods, including water fluoridation, create low levels of fluoride ions in saliva and plaque fluid, thus exerting a topical
Topical
In medicine, a topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.Many topical medications are epicutaneous, meaning that they are applied directly to the skin...
or surface effect. A person living in an area with fluoridated water may experience rises of fluoride concentration in saliva to about 0.04 mg/L several times during a day. Technically, this fluoride does not prevent cavities but rather controls the rate at which they develop. When fluoride ions are present in plaque fluid along with dissolved hydroxyapatite, and the pH is higher than 4.5, a fluorapatite
Fluorapatite
Fluorapatite, often with the alternate spelling of fluoroapatite, is a mineral with the formula Ca53F . Fluorapatite is a hard crystalline solid. Although samples can have various color , the pure mineral is colorless as expected for a material lacking transition metals...
-like remineralized veneer
Veneer (dentistry)
In dentistry, a veneer is a thin layer of restorative material placed over a tooth surface, either to improve the aesthetics of a tooth, or to protect a damaged tooth surface. There are two main types of material used to fabricate a veneer, composite and dental porcelain...
is formed over the remaining surface of the enamel; this veneer is much more acid-resistant than the original hydroxyapatite, and is formed more quickly than ordinary remineralized enamel would be. The cavity-prevention effect of fluoride is mostly due to these surface effects, which occur during and after tooth eruption
Tooth eruption
Tooth eruption is a process in tooth development in which the teeth enter the mouth and become visible. It is currently believed that the periodontal ligaments play an important role in tooth eruption...
. Although some systemic (whole-body) fluoride returns to the saliva via blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
, and to unerupted teeth via plasma or crypt fluid, there is little data to determine what percentages of fluoride's anticavity effect comes from these systemic mechanisms. Also, although fluoride affects the physiology of dental bacteria, its effect on bacterial growth
Bacterial growth
250px|right|thumb|Growth is shown as L = log where numbers is the number of colony forming units per ml, versus T Bacterial growth is the division of one bacterium into two daughter cells in a process called binary fission. Providing no mutational event occurs the resulting daughter cells are...
does not seem to be relevant to cavity prevention.
Fluoride's effects depend on the total daily intake of fluoride from all sources. About 70–90% of ingested fluoride is absorbed
Absorption (Pharmacokinetics)
In pharmacology , absorption is the movement of a drug into the bloodstream.Absorption involves several phases...
into the blood, where it distributes throughout the body. In infants 80–90% of absorbed fluoride is retained, with the rest excreted, mostly via urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
; in adults about 60% is retained. About 99% of retained fluoride is stored in bone, teeth, and other calcium-rich areas, where excess quantities can cause fluorosis. Drinking water is typically the largest source of fluoride. In many industrialized countries swallowed toothpaste is the main source of fluoride exposure in unfluoridated communities. Other sources include dental products other than toothpaste; air pollution from fluoride-containing coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
or from phosphate fertilizers; trona
Trona
Trona ; Na3•2H2O is an evaporite mineral. It is mined as the primary source of sodium carbonate in the United States, where it has replaced the Solvay process used in most of the rest of the world for sodium carbonate production.- Etymology :The word "trona" comes to English by way of either...
, used to tenderize meat in Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
; and tea leaves, particularly the tea brick
Tea brick
Tea bricks or compressed tea are blocks of whole or finely ground black tea, green tea, or post-fermented tea leaves that have been packed in molds and pressed into block form...
s favored in parts of China. High fluoride levels have been found in other foods, including barley, cassava, corn, rice, taro, yams, and fish protein concentrate. The U.S. Institute of Medicine
Institute of Medicine
The Institute of Medicine is a not-for-profit, non-governmental American organization founded in 1970, under the congressional charter of the National Academy of Sciences...
has established Dietary Reference Intake
Dietary Reference Intake
The Dietary Reference Intake is a system of nutrition recommendations from the Institute of Medicine of the U.S. National Academy of Sciences. The DRI system is used by both the United States and Canada and is intended for the general public and health professionals...
s for fluoride: Adequate Intake values range from 0.01 mg/day for infants aged 6 months or less, to 4 mg/day for men aged 19 years and up; and the Tolerable Upper Intake Level is 0.10 mg/kg/day for infants and children through age 8 years, and 10 mg/day thereafter. A rough estimate is that an adult in a temperate climate consumes 0.6 mg/day of fluoride without fluoridation, and 2 mg/day with fluoridation. However, these values differ greatly among the world's regions: for example, in Sichuan, China the average daily fluoride intake is only 0.1 mg/day in drinking water but 8.9 mg/day in food and 0.7 mg/day directly from the air due to the use of high-fluoride soft coal for cooking and drying foodstuffs indoors.
Evidence basis
Existing evidenceEvidence-based medicine
Evidence-based medicine or evidence-based practice aims to apply the best available evidence gained from the scientific method to clinical decision making. It seeks to assess the strength of evidence of the risks and benefits of treatments and diagnostic tests...
strongly suggests that water fluoridation reduces tooth decay. There is also consistent evidence that it causes dental fluorosis
Dental fluorosis
Dental fluorosis is a developmental disturbance of dental enamel caused by excessive exposure to high concentrations of fluoride during tooth development. The risk of fluoride overexposure occurs between the ages of 3 months and 8 years. In its mild forms , fluorosis often appears as unnoticeable,...
, most of which is mild and not usually of aesthetic concern. There is no clear evidence of other adverse effects. Moderate-quality research exists as to water fluoridation's effectiveness and its potential association with cancer; research into other potential adverse effects has been almost all of low quality. Little high-quality research has been performed.
Effectiveness
Water fluoridation is effective at reducing cavities in both children and adults. Earlier studies showed that water fluoridation led to reductions of 50–60% in childhood cavities; more recent studies show lower reductions (18–40%), likely due to increasing use of fluoride from other sources, notably toothpaste, and also to the halo effect of food and drink made in fluoridated areas and consumed in unfluoridated ones.A 2000 systematic review
Systematic review
A systematic review is a literature review focused on a research question that tries to identify, appraise, select and synthesize all high quality research evidence relevant to that question. Systematic reviews of high-quality randomized controlled trials are crucial to evidence-based medicine...
found that water fluoridation was statistically associated
Association (statistics)
In statistics, an association is any relationship between two measured quantities that renders them statistically dependent. The term "association" refers broadly to any such relationship, whereas the narrower term "correlation" refers to a linear relationship between two quantities.There are many...
with a decreased proportion of children with cavities (the median
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
of mean
Mean
In statistics, mean has two related meanings:* the arithmetic mean .* the expected value of a random variable, which is also called the population mean....
decreases was 14.6%, the range
Range (statistics)
In the descriptive statistics, the range is the length of the smallest interval which contains all the data. It is calculated by subtracting the smallest observation from the greatest and provides an indication of statistical dispersion.It is measured in the same units as the data...
−5 to 64%), and with a decrease in decayed, missing
Tooth loss
Tooth loss is when one or more teeth come loose and fall out. Tooth loss is normal for deciduous teeth , when they are replaced by a person's adult teeth. Otherwise, losing teeth is undesirable and is the result of injury or disease, such as mouth trauma, tooth injury, tooth decay, and gum disease...
, and filled
Dental restoration
A dental restoration or dental filling is a dental restorative material used to restore the function, integrity and morphology of missing tooth structure. The structural loss typically results from caries or external trauma. It is also lost intentionally during tooth preparation to improve the...
primary teeth (the median of mean decreases was 2.25 teeth, the range 0.5–4.4 teeth), which is roughly equivalent to preventing 40% of cavities. The review found that the evidence was of moderate quality: many studies did not attempt to reduce observer bias, control for confounding factors, report variance measures, or use appropriate analysis. Although no major differences between natural and artificial fluoridation were apparent, the evidence was inadequate to reach a conclusion about any differences. Fluoride also prevents cavities in adults of all ages. There are fewer studies in adults however, and the design of water fluoridation studies in adults is inferior to that of studies of self- or clinically applied fluoride. A 2007 meta-analysis
Meta-analysis
In statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. In its simplest form, this is normally by identification of a common measure of effect size, for which a weighted average might be the output of a meta-analyses. Here the...
found that water fluoridation prevented an estimated 27% of cavities in adults (95% confidence interval
Confidence interval
In statistics, a confidence interval is a particular kind of interval estimate of a population parameter and is used to indicate the reliability of an estimate. It is an observed interval , in principle different from sample to sample, that frequently includes the parameter of interest, if the...
[CI] 19–34%), about the same fraction as prevented by exposure to any delivery method of fluoride (29% average, 95% CI: 16–42%). A 2002 systematic review found strong evidence that water fluoridation is effective at reducing overall tooth decay in communities.
Most countries in Europe have experienced substantial declines in cavities without the use of water fluoridation. For example, in Finland and Germany, tooth decay rates remained stable or continued to decline after water fluoridation stopped. Fluoridation may be useful in the U.S. because unlike most European countries, the U.S. does not have school-based dental care, many children do not visit a dentist regularly, and for many U.S. children water fluoridation is the prime source of exposure to fluoride. The effectiveness of water fluoridation can vary according to circumstances such as whether preventive dental care is free.
Some studies suggest that fluoridation reduces oral health inequalities between the rich and poor
Economic inequality
Economic inequality comprises all disparities in the distribution of economic assets and income. The term typically refers to inequality among individuals and groups within a society, but can also refer to inequality among countries. The issue of economic inequality is related to the ideas of...
, but the evidence is limited. There is anecdotal but not scientific evidence that fluoride allows more time for dental treatment by slowing the progression of tooth decay, and that it simplifies treatment by causing most cavities to occur in pits and fissures of teeth.
Safety
Dental fluorosis
Dental fluorosis is a developmental disturbance of dental enamel caused by excessive exposure to high concentrations of fluoride during tooth development. The risk of fluoride overexposure occurs between the ages of 3 months and 8 years. In its mild forms , fluorosis often appears as unnoticeable,...
, which can alter the appearance of children's teeth during tooth development
Tooth development
Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. Although many diverse species have teeth, non-human tooth development is largely the same as in humans...
; this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health. The critical period of exposure is between ages one and four years, with the risk ending around age eight. Fluorosis can be prevented by monitoring all sources of fluoride, with fluoridated water directly or indirectly responsible for an estimated 40% of risk and other sources, notably toothpaste, responsible for the remaining 60%. Compared to water naturally fluoridated at 0.4 mg/L, fluoridation to 1 mg/L is estimated to cause additional fluorosis in one of every 6 people (95% CI 4–21 people), and to cause additional fluorosis of aesthetic concern in one of every 22 people (95% CI 13.6–∞ people). Here, aesthetic concern is a term used in a standardized scale based on what adolescents would find unacceptable, as measured by a 1996 study of British 14-year-olds. In many industrialized countries the prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...
of fluorosis is increasing even in unfluoridated communities, mostly because of fluoride from swallowed toothpaste. A 2009 systematic review indicated that fluorosis is associated with consumption of infant formula
Infant formula
Infant formula is a manufactured food designed and marketed for feeding to babies and infants under 12 months of age, usually prepared for bottle-feeding or cup-feeding from powder or liquid . The U.S...
or of water added to reconstitute the formula, that the evidence was distorted by publication bias
Publication bias
Publication bias is the tendency of researchers, editors, and pharmaceutical companies to handle the reporting of experimental results that are positive differently from results that are negative or inconclusive, leading to bias in the overall published literature...
, and that the evidence that the formula's fluoride caused the fluorosis was weak. In the U.S. the decline in tooth decay was accompanied by increased fluorosis in both fluoridated and unfluoridated communities; accordingly, fluoride has been reduced in various ways worldwide in infant formulas, children's toothpaste, water, and fluoride-supplement schedules.
Fluoridation has little effect on risk of bone fracture
Bone fracture
A bone fracture is a medical condition in which there is a break in the continuity of the bone...
(broken bones); it may result in slightly lower fracture risk than either excessively high levels of fluoridation or no fluoridation. There is no clear association between fluoridation and cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
or deaths due to cancer, both for cancer in general and also specifically for bone cancer and osteosarcoma
Osteosarcoma
Osteosarcoma is an aggressive cancerous neoplasm arising from primitive transformed cells of mesenchymal origin that exhibit osteoblastic differentiation and produce malignant osteoid...
. Other adverse effects lack sufficient evidence to reach a confident conclusion. A Finnish study published in 1997 showed that fear that water is fluoridated may have a psychological effect with a large variety of symptoms, regardless of whether the water is actually fluoridated.
Fluoride can occur naturally in water in concentrations well above recommended levels, which can have several long-term adverse effects, including severe dental fluorosis, skeletal fluorosis
Skeletal fluorosis
Skeletal fluorosis is a bone disease caused by excessive consumption of fluoride. In advanced cases, skeletal fluorosis causes pain and damage to bones and joints.-Forms:...
, and weakened bones. The World Health Organization recommends a guideline maximum fluoride value of 1.5 mg/L as a level at which fluorosis should be minimal.
In rare cases improper implementation of water fluoridation can result in overfluoridation that causes outbreaks of acute fluoride poisoning
Fluoride poisoning
In high concentrations, soluble fluoride salts are toxic and skin or eye contact with high concentrations of many fluoride salts is dangerous. Referring to a common salt of fluoride, sodium fluoride , the lethal dose for most adult humans is estimated at 5 to 10 g...
, with symptoms that include nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, and diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
. Three such outbreaks were reported in the U.S. between 1991 and 1998, caused by fluoride concentrations as high as 220 mg/L; in the 1992 Alaska outbreak, 262 people became ill and one person died. In 2010, approximately 60 gallons of fluoride were released into the water supply in Asheboro, North Carolina
Asheboro, North Carolina
Asheboro is a city in Randolph County, North Carolina, United States. The population was 21,672 at the 2000 census. It is the county seat of Randolph County, and is the home of the state-owned North Carolina Zoo.-Geography:...
in 90 minutes—an amount that was intended to be released in a 24-hour period.
Like other common water additives such as chlorine, hydrofluosilicic acid and sodium silicofluoride decrease pH and cause a small increase of corrosivity, but this problem is easily addressed by increasing the pH. Although it has been hypothesized that hydrofluosilicic acid and sodium silicofluoride might increase human lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
uptake from water, a 2006 statistical analysis did not support concerns that these chemicals cause higher blood lead concentrations in children. Trace levels of arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
and lead may be present in fluoride compounds added to water, but no credible evidence exists that their presence is of concern: concentration
Concentration
In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...
s are below measurement limits.
The effect of water fluoridation on the natural environment has been investigated, and no adverse effects have been established. Issues studied have included fluoride concentrations in groundwater and downstream rivers; lawns, gardens, and plants; consumption of plants grown in fluoridated water; air emissions; and equipment noise.
Alternatives
Although water fluoridation is the most effective means of achieving fluoride exposure that is community-wide, other fluoride therapies are also effective in preventing tooth decay; they include fluoride toothpaste, mouthwashMouthwash
Mouthwash or mouth rinse is a product used to enhance oral hygiene. Some manufacturers of mouthwash claim that antiseptic and anti-plaque mouth rinse kill the bacterial plaque causing cavities, gingivitis, and bad breath. Anti-cavity mouth rinse uses fluoride to protect against tooth decay...
, gel, and varnish
Fluoride varnish
Fluoride varnish is a highly concentrated form of fluoride which is applied to the tooth's surface, by a dentist, dental hygienist or other health care professional, as a type of topical fluoride therapy. It is not a permanent varnish but due to its adherent nature it is able to stay in contact...
, and fluoridation of salt and milk. Dental sealant
Dental sealant
Dental sealants are a dental treatment consisting of applying a plastic material to one or more teeth, for the intended purpose of preventing dental caries or other forms of tooth decay.-Development:...
s are effective as well, with estimates of prevented cavities ranging from 33% to 86%, depending on age of sealant and type of study.
Fluoride toothpaste
Toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...
is the most widely used and rigorously evaluated fluoride treatment. Its introduction in the early 1970s is considered the main reason for the decline in tooth decay in industrialized countries, and toothpaste appears to be the single common factor in countries where tooth decay has declined. Toothpaste is the only realistic fluoride strategy in many low-income countries, where lack of infrastructure renders water or salt fluoridation infeasible. However, it relies on individual and family behavior, and its use is less likely among lower economic classes; in low-income countries it is unaffordable for the poor. Fluoride toothpaste prevents about 25% of cavities in young permanent teeth, and its effectiveness is improved if higher concentrations of fluoride are used, or if the toothbrushing is supervised. Fluoride mouthwash and gel are about as effective as fluoride toothpaste; fluoride varnish prevents about 45% of cavities. By comparison, brushing with a nonfluoride toothpaste has little effect on cavities.
The effectiveness of salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
fluoridation is about the same as that of water fluoridation, if most salt for human consumption is fluoridated. Fluoridated salt reaches the consumer in salt at home, in meals at school and at large kitchens, and in bread. For example, Jamaica has just one salt producer, but a complex public water supply; it started fluoridating all salt in 1987, achieving a notable decline in cavities. Universal salt fluoridation is also practiced in Colombia and the Swiss Canton of Vaud; in France and Germany fluoridated salt is widely used in households but unfluoridated salt is also available, giving consumers choice about fluoride. Concentrations of fluoride in salt range from 90 to 350 mg/kg, with studies suggesting an optimal concentration of around 250 mg/kg.
Milk
Milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...
fluoridation is practiced by the Borrow Foundation in some parts of Bulgaria, Chile, Peru, Russia, Macedonia, Thailand and the UK. Depending on location, the fluoride is added to milk, to powdered milk
Powdered milk
Powdered milk is a manufactured dairy product made by evaporating milk to dryness. One purpose of drying milk is to preserve it; milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. Another purpose is to reduce its bulk for...
, or to yogurt. For example, milk-powder fluoridation is used in rural Chilean areas where water fluoridation is not technically feasible. These programs are aimed at children, and have neither targeted nor been evaluated for adults. A 2005 systematic review found insufficient evidence to support the practice, but also concluded that studies suggest that fluoridated milk benefits schoolchildren, especially their permanent teeth.
Other public-health strategies to control tooth decay, such as education to change behavior and diet, have lacked impressive results. Although fluoride is the only well-documented agent which controls the rate at which cavities develop, it has been suggested that adding calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
to the water would reduce cavities further. Other agents to prevent tooth decay include antibacterials such as chlorhexidine and sugar substitutes such as xylitol
Xylitol
Xylitol is a sugar alcohol sweetener used as a naturally occurring sugar substitute. It is found in the fibers of many fruits and vegetables, and can be extracted from various berries, oats, and mushrooms, as well as fibrous material such as corn husks and sugar cane bagasse, and birch...
. Xylitol-sweetened chewing gum
Chewing gum
Chewing gum is a type of gum traditionally made of chicle, a natural latex product, or synthetic rubber known as polyisobutylene. For economical and quality reasons, many modern chewing gums use rubber instead of chicle...
has been recommended as a supplement to fluoride and other conventional treatments if the gum is not too costly. Two proposed approaches, bacteria replacement therapy (probiotics) and caries vaccine
Caries vaccine
A caries vaccine is a vaccine to prevent and protect against tooth decay.Streptococcus mutans has been identified as the major etiological agent of human dental caries.Several types of vaccines are being developed at research centers....
, would share water fluoridation's advantage of requiring only minimal patient compliance, but have not been proven safe and effective. Other experimental approaches include fluoridated sugar, polyphenol
Health effects of polyphenols
Although phenol and its vapors are corrosive to the eyes, skin and respiratory tract, and hydroquinone is also toxic, most other polyphenols do not share the same toxicity and are considered safe for consumption, having long been associated with herbalism...
s, and casein phosphopeptide–amorphous calcium phosphate nanocomplexes
Recaldent
Recaldent, with the technical name casein phosphopeptide – amorphous calcium phosphate, or CPP-ACP, is a milk derived product that strengthens and remineralizes teeth and helps prevent dental caries...
.
A 2007 Australian review concluded that water fluoridation is the most effective and socially the most equitable way to expose entire communities to fluoride's cavity-prevention effects. A 2002 U.S. review estimated that sealants decreased cavities by about 60% overall, compared to about 18–50% for fluoride. A 2007 Italian review suggested that water fluoridation may not be needed, particularly in the industrialized countries where cavities have become rare, and concluded that toothpaste and other topical fluoride offers a best way to prevent cavities worldwide. A 2004 World Health Organization review stated that water fluoridation, when it is culturally acceptable and technically feasible, has substantial advantages in preventing tooth decay, especially for subgroups at high risk.
Economics
Fluoridation costs an estimated $ per person-year on the average (range: $–$; all costs in this paragraph are for the U.S. and are in dollars, inflation-adjusted from earlier estimates). Larger water systems have lower per capita cost, and the cost is also affected by the number of fluoride injection points in the water system, the type of feeder and monitoring equipment, the fluoride chemical and its transportation and storage, and water plant personnel expertise. In affluent countries the cost of salt fluoridation is also negligible; developing countries may find it prohibitively expensive to import the fluoride additive. By comparison, fluoride toothpaste costs an estimated $–$ per person-year, with the incremental cost being zero for people who already brush their teeth for other reasons; and dental cleaning and application of fluoride varnishFluoride varnish
Fluoride varnish is a highly concentrated form of fluoride which is applied to the tooth's surface, by a dentist, dental hygienist or other health care professional, as a type of topical fluoride therapy. It is not a permanent varnish but due to its adherent nature it is able to stay in contact...
or gel costs an estimated $ per person-year. Assuming the worst case, with the lowest estimated effectiveness and highest estimated operating costs for small cities, fluoridation costs an estimated $–$ per saved tooth-decay surface, which is lower than the estimated $ to restore the surface and the estimated $ average discounted
Present value
Present value, also known as present discounted value, is the value on a given date of a future payment or series of future payments, discounted to reflect the time value of money and other factors such as investment risk...
lifetime cost of the decayed surface, which includes the cost to maintain the restored tooth surface. It is not known how much is spent in industrial countries to treat dental fluorosis, which is mostly due to fluoride from swallowed toothpaste.
Although a 1989 workshop on cost-effectiveness
Cost-effectiveness
Cost-effectiveness analysis is a form of economic analysis that compares the relative costs and outcomes of two or more courses of action. Cost-effectiveness analysis is distinct from cost-benefit analysis, which assigns a monetary value to the measure of effect...
of cavity prevention concluded that water fluoridation is one of the few public health measures that save more money than they cost, little high-quality research has been done on the cost-effectiveness and solid data are scarce. Dental sealants are cost-effective only when applied to high-risk children and teeth. A 2002 U.S. review estimated that on average, sealing first permanent molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
saves costs when they are decaying faster than 0.47 surfaces per person-year whereas water fluoridation saves costs when total decay incidence
Incidence (epidemiology)
Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...
exceeds 0.06 surfaces per person-year. In the U.S., water fluoridation is more cost-effective than other methods to reduce tooth decay in children, and a 2008 review concluded that water fluoridation is the best tool for combating cavities in many countries, particularly among socially disadvantaged groups.
U.S. data from 1974–1992 indicate that when water fluoridation is introduced into a community, there are significant decreases in the number of employees per dental firm and the number of dental firms. The data suggest that some dentists respond to the demand shock
Demand shock
In economics, a demand shock is a sudden event that increases or decreases demand for goods or services temporarily. A positive demand shock increases demand and a negative demand shock decreases demand. Prices of goods and services are affected in both cases. When demand for a good or service...
by moving to non-fluoridated areas and by retraining as specialists. U.S. children born 1957–1964 who grew up in fluoridated areas have earned significantly more as adults than children who did not; this effect is heavily concentrated among girls from poorer families, consistent with the hypothesis that the effect is due to consumer and employer discrimination in favor of women with physically more attractive
Physical attractiveness
Physical attractiveness refers to a person's physical traits which are perceived to be aesthetically pleasing or beautiful. The term often implies sexual attractiveness or desirability, but can also be distinct from the two; for example, humans may regard the young as attractive for various...
teeth.
Ethics and politics
Like vaccinationVaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
and food fortification
Food fortification
Food fortification or enrichment is the process of adding micronutrients to food. It can be purely a commercial choice to provide extra nutrients in a food, or sometimes it is a public health policy which aims to reduce numbers of people with dietary deficiencies in a population.Diets that lack...
, fluoridation presents a conflict between benefiting the common good and infringing on individual rights. Fluoridation can be viewed as a violation of ethical
Medical ethics
Medical ethics is a system of moral principles that apply values and judgments to the practice of medicine. As a scholarly discipline, medical ethics encompasses its practical application in clinical settings as well as work on its history, philosophy, theology, and sociology.-History:Historically,...
or legal rules that prohibit medical treatment without medical supervision or informed consent, and that prohibit administration of unlicensed medical substances. It can also be viewed as a public intervention to replicate the benefits of naturally fluoridated water in order to free people from the misery of toothache
Toothache
A toothache, also known as odontalgia or, less frequently, as odontalgy, is an aching pain in or around a tooth.-Causes:* Dental etiology, In most cases toothaches are caused by problems in the tooth or jaw, such as** Dental caries...
and dental work, with greatest benefit to those least able to help themselves, and where it would be unethical to withhold such treatment.
National and international health agencies and dental associations throughout the world have endorsed water fluoridation's safety and effectiveness. The Centers for Disease Control and Prevention listed water fluoridation as one of the ten great public health achievements of the 20th century, alongside vaccination
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
, family planning
Family planning
Family planning is the planning of when to have children, and the use of birth control and other techniques to implement such plans. Other techniques commonly used include sexuality education, prevention and management of sexually transmitted infections, pre-conception counseling and...
, recognition of the dangers of smoking, and other achievements. Other organizations endorsing fluoridation include the World Health Organization, the U.S. Surgeon General, the American Public Health Association
American Public Health Association
The American Public Health Association is Washington, D.C.-based professional organization for public health professionals in the United States. Founded in 1872 by Dr. Stephen Smith, APHA has more than 30,000 members worldwide...
, the European Academy of Paediatric Dentistry, and the national dental associations of Australia, Canada, and the U.S.
Despite support by public health organizations and authorities, efforts to introduce water fluoridation have met considerable opposition, opposition that is "often based on Internet resources or published books that present a highly misleading picture of water fluoridation". Since fluoridation's inception, proponents have argued for scientific optimism and faith in experts, while opponents have drawn on distrust of experts and unease about medicine and science. Controversies include disputes over fluoridation's benefits and the strength of the evidence basis for these benefits, the difficulty of identifying harms, legal issues over whether water fluoridation is a medicine, and the ethics of mass intervention. U.S. opponents of fluoridation were heartened by a 2006 National Research Council
United States National Research Council
The National Research Council of the USA is the working arm of the United States National Academies, carrying out most of the studies done in their names.The National Academies include:* National Academy of Sciences...
report about hazards of water naturally fluoridated to high levels; the report recommended lowering the U.S. maximum limit of 4 mg/L for fluoride in drinking water. Opposition campaigns involve newspaper articles, talk radio, and public forums. Media reporters are often poorly equipped to explain the scientific issues, and are motivated to present controversy regardless of the underlying scientific merits. Internet websites, which are increasingly used by the public for health information, contain a wide range of material about fluoridation ranging from factual to fraudulent, with a disproportionate percentage opposed to fluoridation. Antifluoridationist literature links fluoride exposure to a wide variety of effects, including AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...
, allergy
Allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...
, Alzheimer's, arthritis
Arthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....
, cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, and low IQ, along with diseases of the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
, kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, pineal gland
Pineal gland
The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions...
, and thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...
.
Conspiracy theories involving fluoridation are common, and include claims that fluoridation was motivated by protecting the U.S. atomic bomb program from litigation, that (as famously parodied in the film Dr. Strangelove) it is part of a Communist or New World Order plot to take over the world, that it was pioneered by a German chemical company to make people submissive to those in power, that behind the scenes it is promoted by the sugary food or phosphate fertilizer or aluminum industries, or that it is a smokescreen to cover failure to provide dental care to the poor. One such theory is that fluoridation was a public-relations ruse sponsored by fluoride polluters such as the aluminum maker Alcoa
Alcoa
Alcoa Inc. is the world's third largest producer of aluminum, behind Rio Tinto Alcan and Rusal. From its operational headquarters in Pittsburgh, Pennsylvania, Alcoa conducts operations in 31 countries...
and the Manhattan Project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...
, with conspirators that included industrialist Andrew Mellon and the Mellon Institute's researcher Gerald J. Cox, the Kettering Laboratory of the University of Cincinnati
University of Cincinnati
The University of Cincinnati is a comprehensive public research university in Cincinnati, Ohio, and a part of the University System of Ohio....
, the Federal Security Agency
Federal Security Agency
The Federal Security Agency was an independent agency of the United States government established in 1939 pursuant to the "Reorganization Act of 1939"...
's administrator Oscar R. Ewing, and public-relations strategist Edward Bernays
Edward Bernays
Edward Louis Bernays , was an Austrian-American pioneer in the field of public relations and propaganda along with Ivy Lee, referred to in his obituary as "the father of public relations"...
. Specific antifluoridation arguments change to match the spirit of the time.
Opponents of fluoridation include some researchers, dental and medical professionals, alternative medical practitioners such as chiropractors, and health food enthusiasts; a few religious objectors, mostly Christian Scientists in the U.S.; and occasionally consumer groups and environmentalists. Organized political opposition has come from right-wing groups such as the John Birch Society
John Birch Society
The John Birch Society is an American political advocacy group that supports anti-communism, limited government, a Constitutional Republic and personal freedom. It has been described as radical right-wing....
, libertarians, and from left-wing groups like Green parties in the UK and New Zealand. Many people do not know that fluoridation is meant to prevent tooth decay, or that natural or bottled water can contain fluoride; as the general public does not have a particular view on fluoridation, the debate may reflect an argument between two relatively small lobbies
Lobbying
Lobbying is the act of attempting to influence decisions made by officials in the government, most often legislators or members of regulatory agencies. Lobbying is done by various people or groups, from private-sector individuals or corporations, fellow legislators or government officials, or...
for and against fluoridation. A 2009 survey of Australians found that 70% supported and 15% opposed fluoridation; those opposed were much more likely to score higher on outrage factor
Outrage factor
In public policy, the outrage factor is the portion of public opposition to a policy which does not derive from knowledge of the technical details...
s such as "unclear benefits". A 2003 study of focus groups from 16 European countries found that fluoridation was opposed by a majority of focus group members in most of the countries, including France, Germany, and the UK. A 1999 survey in Sheffield
Sheffield
Sheffield is a city and metropolitan borough of South Yorkshire, England. Its name derives from the River Sheaf, which runs through the city. Historically a part of the West Riding of Yorkshire, and with some of its southern suburbs annexed from Derbyshire, the city has grown from its largely...
, UK found that while a 62% majority favored water fluoridation in the city, the 31% that were opposed expressed their preference
Willingness to pay
In economics, the willingness to pay is the maximum amount a person would be willing to pay, sacrifice or exchange in order to receive a good or to avoid something undesired, such as pollution...
with greater intensity than supporters. A 2007 Scottish bioethics
Bioethics
Bioethics is the study of controversial ethics brought about by advances in biology and medicine. Bioethicists are concerned with the ethical questions that arise in the relationships among life sciences, biotechnology, medicine, politics, law, and philosophy....
council report concluded that good evidence for or against water fluoridation is lacking, therefore local and regional democratic procedures are the most appropriate way to decide whether to fluoridate. Every year in the U.S., pro- and anti-fluoridationists face off in referenda or other public decision-making processes: in most of them, fluoridation is rejected. In the U.S., rejection is more likely when the decision is made by a public referendum; in Europe, most decisions against fluoridation have been made administratively. Neither side of the dispute appears to be weakening or willing to concede.
Use around the world
In addition, at least 50 million people worldwide drink water that is naturally fluoridated to optimal levels; the actual number is unknown and is likely to be much higher. Naturally fluoridated water is used in many countries, including Argentina, France, Gabon, Libya, Mexico, Senegal, Sri Lanka, Tanzania, the U.S., and Zimbabwe. In some locations, notably parts of Africa, China, and India, natural fluoridation exceeds recommended levels; in China an estimated 200 million people receive water fluoridated at or above recommended levels.
Communities have discontinued water fluoridation in some countries, including Finland, Germany, Japan, the Netherlands, Sweden, and Switzerland. This change was often motivated by political opposition to water fluoridation, but sometimes the need for water fluoridation was met by alternative strategies. The use of fluoride in its various forms is the foundation of tooth decay prevention throughout Europe; for example, France, Germany, and many other European countries use fluoridated salt.
History
The history of water fluoridation can be divided into three periods. The first was research into the cause of a form of mottled tooth enamel called the Colorado brown stain. The second (c. 1933–1945) focused on the relationship between fluoride concentrations, fluorosis, and tooth decay, and established that moderate levels of fluoride prevent cavities. The third period, from 1945 on, focused on adding fluoride to community water supplies.
The foundation of water fluoridation in the U.S. was the research of the dentist Frederick McKay. McKay spent thirty years investigating the cause of what was then known as the Colorado brown stain, which produced mottled but also cavity-free teeth; with the help of G.V. Black and other researchers, he established that the cause was fluoride. The first report of a statistical association between the stain and lack of tooth decay was made by UK dentist Norman Ainsworth in 1925. In 1931, an Alcoa
Alcoa
Alcoa Inc. is the world's third largest producer of aluminum, behind Rio Tinto Alcan and Rusal. From its operational headquarters in Pittsburgh, Pennsylvania, Alcoa conducts operations in 31 countries...
chemist, H.V. Churchill, concerned about a possible link between aluminum and staining, analyzed water from several areas where the staining was common and found that fluoride was the common factor.
Grand Rapids, Michigan
Grand Rapids is a city in the U.S. state of Michigan. The city is located on the Grand River about 40 miles east of Lake Michigan. As of the 2010 census, the city population was 188,040. In 2010, the Grand Rapids metropolitan area had a population of 774,160 and a combined statistical area, Grand...
, starting January 25, 1945. The results, published in 1950, showed significant reduction of cavities. Significant reductions in tooth decay were also reported by important early studies outside the U.S., including the Brantford–Sarnia–Stratford study in Canada (1945–1962), the Tiel–Culemborg study in the Netherlands (1953–1969), the Hastings study in New Zealand (1954–1970), and the Department of Health study in the U.K. (1955–1960). By present-day standards these and other pioneering studies were crude, but the large reductions in cavities convinced public health professionals of the benefits of fluoridation.
Fluoridation became an official policy of the U.S. Public Health Service by 1951, and by 1960 water fluoridation had become widely used in the U.S., reaching about 50 million people. By 2006, 69.2% of the U.S. population on public water systems were receiving fluoridated water, amounting to 61.5% of the total U.S. population; 3.0% of the population on public water systems were receiving naturally occurring fluoride. In some other countries the pattern was similar. New Zealand, which led the world in per-capita sugar consumption and had the world's worst teeth, began fluoridation in 1953, and by 1968 fluoridation was used by 65% of the population served by a piped water supply. Fluoridation was introduced into Brazil in 1953, was regulated by federal law starting in 1974, and by 2004 was used by 71% of the population. In the Republic of Ireland, fluoridation was legislated in 1960, and after a constitutional challenge the two major cities of Dublin and Cork began it in 1964; fluoridation became required for all sizeable public water systems and by 1996 reached 66% of the population. In other locations, fluoridation was used and then discontinued: in Kuopio
Kuopio
Kuopio is a city and a municipality located in the region of Northern Savonia, Finland. A population of makes it the ninth biggest city in the country. The city has a total area of , of which is water and half forest...
, Finland, fluoridation was used for decades but was discontinued because the school dental service provided significant fluoride programs and the cavity risk was low, and in Basle, Switzerland, it was replaced with fluoridated salt.
McKay's work had established that fluorosis occurred before tooth eruption
Tooth eruption
Tooth eruption is a process in tooth development in which the teeth enter the mouth and become visible. It is currently believed that the periodontal ligaments play an important role in tooth eruption...
. Dean and his colleagues assumed that fluoride's protection against cavities was also pre-eruptive, and this incorrect assumption was accepted for years. By 2000, however, the topical effects of fluoride (in both water and toothpaste) were well understood, and it had become known that a constant low level of fluoride in the mouth works best to prevent cavities.