FLUORIDE

FLUORIDE. Fluoride is an important trace element in human nutrition. Daily exposure to small quantities is widely considered to be vital for maintenance of sound tooth structure. Ingested or systemic fluoride has long been known to offer significant benefit when supplied during tooth formation in childhood. More recently, topical exposure (that is, making fluoride available at the tooth surface) has been shown to provide benefits throughout life, even for older adults.

Sources of Fluoride

Water, rocks, soil, and living tissue all have naturally occurring fluoride as a constituent. Crystalline and carbonate minerals containing fluoride are common throughout the earth's near-surface crust. As water flows through the environment, fluoride and many other ions dissolve from sedimentary rock layers and soil into aquifers, streams, rivers, and oceans. Dissolved ions are essential for humans and all living things. Fluoride ions are absorbed directly from the water we drink.

Fluoride in Bone and Tooth Tissue

Fluoride ions taken systemically can become incorporated within bone and tooth tissue. Although bones and teeth have an organic matrix, it is their inorganic or crystalline hydroxyapatite composition that gives them their strength and hardness. Living human cells use available calcium and other minerals to form strong hydroxyapatite matrices. When fluoride ions are also available to the cells, an additional material called fluorapatite is formed. Integration of a small amount of fluorapatite within a hydroxyapatite matrix may produce a more durable substance than is found with hydroxyapatite alone.

Topical Mechanism

Fluoride ions can also provide a very strong surface or topical effect for teeth when available on a regular basis. One such effect is that topical fluoride inhibits the ability of some bacteria to produce dental plaque by blocking the function of important intracellular bacterial enzymes. Much more significantly, topical fluoride also leads to reduced demineralization and increased remineralization of enamel surfaces.

Bacterial Acid and Chemical Balance

Demineralization of a tooth occurs when bacteria create an acidic or low pH environment at the tooth surface. The acidity dissolves hydroxyapatite, releasing positively charged calcium ions and negatively charged carbonate and phosphate ions into saliva. When normal saliva flow dilutes the acidity, the positive and negative ions recombine and remineralize the surface.

This cycle represents a balance. Diets rich in fermentable carbohydrates such as mono-and disaccharides, which are relatively simply sugars, disrupt the balance. They stimulate some oral bacteria to produce dental plaque and acid. Dental plaque is a substance that attaches to tooth enamel and is colonized by the bacteria that form it. Once such a colony is established, each ingestion of fermentable carbohydrate causes approximately one half-hour of intense acid production by the bacteria. This burst of acid production lowers the pH near the tooth surface, demineralizing large amounts of hydroxyapatite. The balance is disrupted and, as the cycle is repeated, it damages the tooth's surface.

Topical Fluoride and Stronger Enamel

When sufficient amounts of negatively charged fluoride ions are routinely present topically at the tooth surface, a different pattern emerges for this cycle. The balance of demineralization and remineralization actually builds fluoride into the tooth's surface structure. Over long exposure to fluoride in saliva, more and more fluoride is incorporated, and the enamel surface becomes stronger. A much greater increase in acidity is then necessary before a destructive imbalance in the cycle will be initiated. This surface or topical effect is thought to be the primary means by which fluoride prevents dental caries.

Benefits of Community Water Fluoridation

In studies of many communities over several decades, it has become clear that there is great benefit to maintaining proper fluoride levels in the public water supply. A concerted public health effort throughout the decades since the 1950s has led to the maintenance of fluoride at these levels in many public water supplies.

Community water fluoridation is intended to provide fluoride at concentrations ranging from 0.7 to 1.2 ppm. Coincidentally, this is about the same concentration of fluoride that is found in ocean water. Levels are adjusted within this range regionally and throughout the year. This provides lower concentrations of fluoride when people are likely to drink more water and higher concentrations when less water consumption is expected.

Without other significant sources of fluoride during the 1950s and 1960s, community water fluoridation produced reductions of 40 to 50 percent in the number of cavities or dental caries among children. Their teeth had enamel that was more resistant to caries both when it was formed and throughout life.

Other countries have assessed a variety of alternative means for delivering protective levels of fluoride. These have included supplementation with tablets or drops, salt fluoridation, and milk fluoridation. However, in the United States, fluoridation of public water as part of purification treatment remains the most effective and economical means for providing this benefit to communities. Currently about 60 percent of the U.S. population has fluoride maintained at these levels in their drinking water.

In the 1980s, it became clear that the positive effects of water fluoridation were not limited to developing teeth. Studies of people age sixty-five and older showed that it was beneficial even when all of the fluoride exposure took place after tooth eruption. Those who lived in communities with fluoridated water as adults had significantly lower rates of dental caries on exposed tooth root surfaces than comparable older adults without fluoridated water.

Fluoride and Osteoporosis

There has been interest in potential positive effects of fluoride supplementation on increased bone density. When ingested, fluoride is absorbed primarily from the upper gastrointestinal tract and is excreted in urine. Fluoride that is not excreted is deposited in calcified tissues—bones and teeth.

Osteoporosis, loss of bone density, is an increasingly prevalent problem in the U.S. population among both men and women. Unfortunately, research to date does not suggest a useful effect of fluoride on bone strength, even when it is supplemented at concentrations twenty times greater than that found in fluoridated water.

Early Research on Fluoride

It was research on the effects of prolonged intake of excessive amounts of naturally occurring fluoride that led scientists to understand the protection afforded by healthy fluoride levels. In the 1930s, a dentist in Colorado, Dr. Frederick McKay, became curious about a brown surface stain seen on some of his patients' teeth. These teeth often had a rough and porous surface texture, yet they were also far less prone to develop dental caries.

McKay's early observations led to a long series of investigations. It became clear that this problem, a severe form of fluorosis, resulted from very high levels of naturally occurring fluoride in drinking water. McKay's water samples had fluoride concentrations as much as fourteen times greater than that recommended today for community water systems. These investigations led to the discovery that when fluoride was present at the low levels that are now widely used, it offered powerful protection from dental caries without any adverse effects.

Reevaluation of Fluoride Use

By the 1990s, the wide availability of fluoridated water led scientists to reevaluate fluoride use practices. Particular attention was paid to the potential for a diffuse exposure to fluoride throughout the population. Many packaged foods are processed in communities with fluoridated water, becoming sources of small amounts of fluoride to those who consume them. Far more important, however, is the use of toothpaste and other products containing fluoride. It was concluded that community water fluoridation levels remain appropriate, but that greater care must be taken in the use of fluoride toothpaste.

Levels of fluoride in treated drinking water are extremely low when compared to concentrations in common therapeutic products. For example, fluoride concentration in over-the-counter fluoride mouth rinses is generally about 230 parts per million (ppm); toothpastes contain about 1,000 ppm; prescription home-use mouth rinses and home-use gels range from 1,000 to 5,000 ppm; professionally applied fluoride gels contain 10,000 to 12,300 ppm; and professionally applied fluoride varnishes contain about 22,000 ppm.

The additional sources of fluoride, primarily toothpaste, have led to lower rates of dental caries in U.S. communities not provided with fluoridated water. However, even with these lower background rates of dental caries in the population, it is estimated that community water fluoridation alone still provides an additional reduction of 20 to 40 percent in dental caries when comparison is made to caries rates for Americans who do not have fluoridated water but who use fluoride toothpaste.

Fluoride Issues for the Future

During the reevaluation of fluoride in the 1990s, concerns were raised regarding the potential for fluorosis. In contemporary studies of fluorosis in the U.S. population, nearly all observed cases have been classified as "very mild" or "mild." These are categories of "white-spot" discoloration that are usually only apparent to a dentist conducting an intraoral examination. Ingestion of fluoride toothpaste is considered the primary explanation for these white-spot discolorations.

Children are likely to swallow toothpaste while brushing, ingesting an unintended and excessive amount of fluoride. The most effective strategy for avoiding mild fluorosis is to limit children to a pea-sized quantity of toothpaste at each brushing. This quantity is adequate for caries prevention and oral hygiene, but it should not lead to development of fluorosis.

Use of infant formula and some baby foods has also raised a degree of concern. Because of infants' very small body mass, the proper intake of systemic fluoride is lower than that for slightly older children. Some studies have identified varying levels of fluoride in these products, some approaching levels that are associated with increased risk for very mild or mild fluorosis in infants. Physicians and dentists are urged to use caution in prescribing fluoride supplements for infants and very young children living in communities without fluoridated water because they might be consuming these fluoride-containing products.

The U.S. Environmental Protection Agency has set a standard of 4.0 ppm as the maximum allowable fluoride level in drinking water. Within the United States, fluoride levels in drinking water are actually maintained at about one-fourth of this level. However, in some developing countries, particularly in southern Asia and northern Africa, natural fluoride is present at extremely high levels. In India, for example, a study sponsored by the World Health Organization found natural fluoride levels exceeding 1.5 ppm in about 8 percent of samples, with some concentrations as high as 22.0 ppm. In such areas, public health workers actively engage in efforts to reduce fluoride exposure and eliminate fluorosis.

Conclusion

Nearly one hundred organizations with related expertise, including the World Health Organization, the U.S. Public Health Service, the American Medical Association, the American Public Health Association, the American Society for Clinical Nutrition, the American Society for Nutritional Sciences, the International Association for Dental Research, the FDI World Dental Federation, and the American Cancer Society have recognized the importance of daily fluoride intake for dental health. Particularly when supplied through community water fluoridation, ensuring adequate dietary fluoride exposure has been an extremely safe and cost-effective public health measure. Fluoride is a trace element that has extremely important personal and public health benefits for promotion and maintenance of optimal oral health.

See also Dentistry ; Digestion .

BIBLIOGRAPHY

American Dental Association. "Statement on Water Fluoridation Efficacy and Safety." Available at http://www.ada.org/prof/prac/issues/statements/fluoride2.html.

American Dental Association. "Fluoride and Fluoridation."Available at http://www.ada.org/public/topics/fluoride/facts-intro.html.

American Dietetic Association. "Position of the American Dietetic Association: The Impact of Fluoride on Health." Journal of the American Dietetic Association 100 (2000): 1208–1213.

Burt, Brian A., and Stephen A. Eklund. Dentistry, Dental Practice, and the Community 5th ed. Philadelphia: W.B. Saunders, 1999.

Clarkson, John J., and Jacinta McLoughlin. "Role of Fluoride in Oral Health Promotion." International Dental Journal 50 (2000): 119–128.

Ekstrand, J., and A. Oliveby. "Fluoride in the Oral Environment." Acta Odontologica Scandinavica 57 (1999): 330–333.

Gillcrist, James A., David E. Brumley, and Jennifer U. Blackford. "Community Fluoridation Status and Caries Experience in Children." Journal of Public Health Dentistry 61 (2001): 168–171.

Griffin, S. O., K. Jones, and S. L. Tomar. "An Economic Evaluation of Community Water Fluoridation." Journal of Public Health Dentistry 61 (2001): 78–86.

International Collaborative Research on Fluorides: Research Needs Workshop, sponsored by the National Institute of Dental and Craniofacial Research, May 1999. "International Collaborative Research on Fluoride." Journal of Dental Research 79 (2000): 893–904.

National Institutes of Health (NIH). "Diagnosis and Management of Dental Caries Throughout Life." Consensus Statement 2001, March 26–28, Vol. 18, No. 1.

Office of the Surgeon General. Oral Health in America: A Report of the Surgeon General. Rockville, Md.: U.S. Department of Health and Human Services, 2000.

Stephen, K. W. "Fluoride Prospects for the New Millennium: Community and Individual Patient Aspects." Acta Odontologica Scandinavica 57 (1999): 352–355.

ten Cate, J. M., and Cor van Loveren. "Fluoride Mechanisms." Dental Clinics of North America 43 (1999): 713–742.

Warren, John J., and Steven M. Levy. "Systemic Fluoride: Sources, Amounts, and Effects of Ingestion." Dental Clinics of North America 43 (1999): 695–711.

Rob Berg

Fluoride Treatment

Background

A fluoride treatment is a mineral solution applied to teeth in order to strengthen them and help prevent cavities. Fluoride containing products include commercially available toothpaste and mouth rinse, as well as more concentrated liquids and gels used professionally by dentists.

There are three primary factors that contribute to dental caries (tooth decay): a susceptible site on a tooth, an infective strain of bacteria (Streptococcus mutans), and sugars or other nutrients that stimulate the bacteria's growth. As these bacteria grow, they produce an acidic byproduct that can dissolve the minerals in the enamel and eventually destroy the tooth.

Dentists largely credit the use of fluoride treatments and fluoridated water with the drastic decline in tooth decay over the past several decades. One report indicates that for children ages 5-7 years old in the United States the average incidence of cavities has dropped from 7.1% in the 1970s to 2.5% in the 1990s. Similar improvements have been documented across almost all age groups. Still, tooth decay remains the most common infectious childhood disease and fluoride treatments remain an important tool in the fight against cavities.

Fluoride is actually a form of the element fluorine. In its elemental form fluorine is a toxic gas, but when it is chemically reacted with other compounds, such as tin, it takes on new cavity fighting uses. Once in the mouth, fluoride is diluted in saliva and deposited in bacterial plaque on the surface of the teeth. Here it works to protect the tooth in two ways. First, it directly inhibits bacterial growth so less acid is produced in the mouth. Second, the fluoride stored in plaque is released when the bacteria produce enough acid to lower the acid-base balance on the tooth. When this occurs fluoride diffuses into the tooth through tiny pores in the enamel. Fluoride ions replace the hydroxyl ions of the hydroxyapatite crystals, which are part of the tooth's enamel, and form a new compound called fluorapatite. This form of enamel is less soluble in the acids produced by oral bacteria and therefore helps protect teeth from decay.

History

Frederick S. McKay, a dentist practicing in Colorado Springs, Colorado in the early 1900s, was the first to discover that fluoride is an effective cavity fighter. McKay noticed that many of his patients had mottled enamel, or brown stains, on their teeth. By 1916, McKay and his researchers had found that the mottling was caused by something in the patients' drinking water. It took him 12 more years to understand how this effect was related to caries, and another three years to recognize the chemical mechanism causing this change. Finally, in 1931 in McKay verified that patients with mottled teeth were drinking water with unusually high levels of naturally occurring fluoride. This connection was studied in more detail throughout the 1930s and 1940s, culminating in the determination that one part per million was the ideal level of fluoride in drinking water, substantially reducing decay while not causing mottling.

This research led to the implementation of a fluoridation program by the federal government, and by the early 1950s most United States communities with a public water sys-tem had adopted fluoride treated water. The idea of using fluoride in oral care products began in 1956 when Procter and Gamble launched "Crest with Fluoristan." Since the 1950s, scores of fluoride containing products have been introduced both for the general market and for dental professionals.

Even though fluoride has been used for decades, there are still concerns about its health effects today. Although the chemistry is not fully understood, researchers believe that high levels of fluoride can interrupt the natural formation of tooth enamel. They theorize that too much fluoride creates a hypomineralization, which leads to the chalky, cloudy, or opaque appearance that is characteristic of fluorosis. While dental proponents claim that fluoride is largely responsible for improved dental health, there are those who claim that it can cause a form of bone cancer. In the 1980s a study conducted by the National Toxicology Program found "equivocal evidence" of carcinogenicity based on testing done on rats. However, the panel eventually concluded that there was no solid data linking cancer, including osteosarcoma, directly to fluoridation.

Both United States and British Dental Associations continue to recommend that both adults and children brush twice daily with fluoride toothpaste, but they also recommend that to reduce the risk of fluorosis, children should not swallow the toothpaste. The subject remains a hot topic of political debate.

Raw Materials

There are a variety of fluoride compounds that are allowed by the Food and Drug Administration (FDA) for use in oral care products. Fluoride ingredients are listed according to the type of product in which they may be used and by the percentage that must be included in the formula.

Toothpaste. Sodium fluoride: 0.22%; sodium monofluorophosphate: 0.76%; stannous fluoride: 0.4%.

Treatment rinse. (The pH, or acid-base balance, of the formula can affect the functionality of the fluoride. The higher the pH of the product the more acid it contains. The lower the pH, the more basic it is.) Sodium fluoride acidulated with a mixture of sodium phosphate, monobasic, and phosphoric acid to a level of 0.1 molar phosphate ion and a pH of 3.0—4.5, which yields an effective fluoride ion concentration of 0.02%; sodium fluoride acidulated with a mixture of sodium phosphate, diabasic, and phosphoric acid to a pH of 3.5, which yields an effective fluoride ion concentration of 0.01%; sodium fluoride 0.02% aqueous solution with a pH of approximately 7; sodium fluoride 0.05% aqueous solution with a pH of approximately 7; sodium fluoride concentrate containing adequate directions for mixing with water before using to result in a 0.02% or 0.05% aqueous solution with a pH of approximately 7; stannous fluoride concentrate marketed in a stable form and containing adequate directions for mixing with water immediately before using to result in a 0.1% aqueous solution.

Treatment gel. Stannous fluoride: 0.4%.

In addition to fluoride, these products contain a variety of other ingredients including solvents, thickeners, and pH control agents. Solvents include water or glycerine, which are used as a carrier for reasons of efficacy, safety, and cost. Deionized or demineralized water is used to prevent unwanted minerals from affecting the performance or stability of the product. The concentration of water in the formula may be 90% or more.

Thickening agents are added to control viscosity. These include xanthan, carrageenan, and various other gums and polymers used at concentrations between 0.1-2.0%.

Flavors and colors are added to make the products more appealing. Popular flavors include mint, bubble gum, and grape, and these are added at a few tenths of a percent. Dyes are used to impart color at very low levels (less than a hundredth of a percent). Since the product may be swallowed accidentally these dyes must be approved for use in food products.

Preservatives are added when necessary. Depending on the pH of the product, they may be required to prevent the growth of mold or bacteria in the product while it is stored the shelf. One or two tenths of a percent is a typical use level for a preservative.

Organic acids, such as phosphoric acid, may be added to control the product's pH. Some forms of fluoride require a low pH to be functional. These are added at a few tenths of a percent as well.

Design

Fluoride treatments are designed to provide an appropriate concentration of fluoride at a pH level that will help the correct amount of fluoride deposit on the teeth. If the fluoride level is too low the treatment will not be effective; if it is too high the patients might accidentally be poisoned. In the United States, laws have been created to ensure that these products are safe and efficacious. The FDA regulates them as either over-the-counter (OTC) drugs or as professional products for use by dentists. In addition, the FDA limits the size of commercially available products to reduce the possibility of accidental overdose. Finally, the organization determines labeling requirements for all commercial products and some aspects of professional ones. These requirements most be taken into consideration when designing fluoride treatments.

OTC fluoride-containing drugs include toothpaste and mouth rinse. Professional products are more concentrated and may be applied either as a gel, foam, or liquid. They may be designed to be applied using plastic trays that fit around the teeth. Depending on the type of product being formulated, the development chemist can choose from several types of FDA approved actives. Once again, these regulatory factors must be considered in product design.

Key examples of treatment formulations are: acidulated phosphate fluoride gel with 1.23% fluoride ion at pH 3.5, designed to flow easily during tray placement yet thickens during treatment so it does not drip down the patient's throat; sodium fluoride gel with 2% fluoride ion at pH 7.0, for use when etching of porcelain restorations is a concern; stannous fluoride liquid rinse with 0.63% fluoride ion, designed to prevent decay, reduce plaque accumulation, and help reduce gingival inflammation and bleeding; APF fluoride foam with 1.23% fluoride ion at pH 3-4.25, designed as an easy to use non-aerosol foam that reduces accidental ingestion by the patient.

The Manufacturing
Process

Batching

• 1 The process of manufacturing a fluoride containing treatment is similar to the processes used to make other oral care products. Because most of the fluoride compounds used in treatments are water-soluble, these products are relatively easy to make. The manufacturing process involves simple mixing and does not require any special solvents or emulsification. Large batches can be made in stainless steel tanks as large as 3,000 gal (11,356 1). The first step is to charge the batch tank with water or glycerine, which makes up the largest percentage of the formula. The water is stirred with an electrically driven turbine mixer. The mixing speed is computer controlled to optimize the stirring conditions when other ingredients are added. While manufacturing procedures vary widely, it is common to add the color early in the batching process. The dyes that are used in these products are highly concentrated and if too much dye is added by mistake it is easier and cheaper to dispose of the batch before the more expensive ingredients have been added.
• 2 The other ingredients may be added in succession. Depending on the solubility of the form of fluoride chosen, heating and cooling may be required to help dissolve the powders quickly. During this batching process samples may be taken periodically during the mixing process to check for clarity. Toward the end of the batching process the pH control agents are introduced. They ensure the batch has the proper acid base balance. Flavors are added at the end of the operation if they are heat sensitive.

Batch check

• 3 Once the batch is complete, it must be evaluated to ensure it is within specification. It is particularly important to ensure that the active ingredients are present at their designated concentrations. Tests such as pH analysis, weight percentage of solids, and fluoride concentration are used to maintain product specifications.

Filling operations

• 4 Once the batch is finished and approved, the filling operation can proceed. Depending on the nature of the process, the batch may be filled directly from the batch tank or it may be transferred to a secondary vessel or holding tank. High speed filling equipment is used but the filling speed depends on the product's viscosity. Thin, liquid products can be filled faster and more efficiently than thicker gels.
• 5 The filled package is fed down an assembly line where the closure is attached. While a bottle may only require a simple cap to seal it, products packed in tubes or foaming dispensers may involve more complicated sealing mechanisms. After the package has been filled and closure has been attached, the unit is ready for final packing. Multiple units may be shrink wrapped together or placed in cartons for shipping.

Quality Control

In addition to the chemical tests conducted during the manufacturing process, fluoride treatments are subject to special testing considerations to establish product performance. Historically these tests have involved expensive human clinical studies, but since 1988 the Dental Panel has allowed the use of new laboratory tests to determine the efficiency of fluoride treatments.

The Future

While the political future of fluoride treatments may be uncertain, they continue to be an important tool in the fight against cavities. There are new technological advances that may some day lead to fluoride free cavity fighters. British researchers have discovered a new kind of anti-caries agent that stops tooth decay for up to three months. Their new ingredient is a protein fragment, called peptide p1025 that works by attaching itself to the tooth surfaces where cavity-causing bacteria normally bind. The protein blocks the bacteria from attaching to teeth so they are easily washed away. Breakthroughs like this could someday provide fluoride-free ways to prevent tooth decay.

Where to Learn More

Books

Wolinsky, L. E. "Caries and Cariology." In Oral Microbiology and Immunology. 2nd ed. Ed. R. J. Nisengard and M. G. Newman. Philadelphia: W. B. Saunders Company, 1994.

Periodicals

Brady, Robert P., and Abbe Goldstein. "Keeping Faith in Fluoride." Chemist & Druggist (24 May 1997): 24.

"Mouthwash Cancels Cavities." Popular Mechanics (February 2000): 15.

"Postmenopausal Osteoporosis Treatment with Fluoride." American Family Physician (January 1996): 302.

Sheikh, Aamir, and Alice M. Horowitz. "Benefits of Fluoride Toothpaste." Journal of School Health (October 1999): 299.

Other

Connelly. "Caries Treatment with Fluoride." United States Patent 5738113, 1998.

RandySchueller

Fluoride

Definition

Purpose

Description

Precautions

Interactions

Complications

Parental concerns

Resources

Definition

Fluoride is a naturally occurring element found in water and food. It is important for the development of strong bones and teeth.

Purpose

In addition to occurring naturally in some water, fluoride is added to toothpastes, mouthwashes, and some public water supplies to prevent tooth decay (dental caries).

Description

Fluoride is found naturally in seawater and in some drinking water and is present in small amounts in almost all soil, plants, and animals. In water, fluoride dissolves to form a negatively charged ion (F^-). In the body, this ion is absorbed into the bloodstream from the small intestine. It then binds with calcium in bones and teeth. The adult body contains less than one-tenth of one ounce (about 2.5 g) of fluoride. Ninety-five percent of this is found in bones and teeth.

The importance of fluoride for dental health has been recognized since the 1930s when an association between the fluoride content of drinking water and the prevalence of dental caries was first noted. Acids found in food or released by bacteria that feed on sugar in the mouth cause tooth erosion. These acids eat away at the enamel on the surface of the tooth. Fluoride prevents tooth decay two ways. First, the fluoride in saliva reacts with calcium and phosphate in teeth to repair damage to the tooth’s surface. The new surface formed when the tooth is repaired is stronger than the original enamel and is better able to resist decay. This process is called tooth remineral-ization. Second, fluoride interferes with the metabolic.

Suggested amounts of dietary fluoride supplements

* 1.0 part per million (ppm)= 1 milligram/liter (mg/L)

** 2.2 mg sodium fluoride contains 1 mg fluoride ion

source: American Dental Association

It is suggested that children between the ages of 6 months to 16 years living in non-fluoridated areas use dietary fluoride supplements. Your dentist can prescribe the correct dosage for your child based on the level of fluoride in your drinking water. (Illustration by GGS Information Services/Thomson Gale.)

processes of bacteria in the mouth so that they produce less decay-causing acid.

Since teeth containing fluoride become stronger, some researchers have suggested that fluoride might also make bones stronger and prevent or delay osteoporosis (age related thinning of the bones). These researchers have generally found that the amount of fluoride that prevents tooth decay does not affect the strength or density of bones. High doses of fluoride are potentially toxic, and very large doses (5–15 times the daily adequate intake) taken over time cause bones to become chalky and brittle. Consequently, researchers have concluded that fluoride supplements are not an appropriate way to prevent or treat osteoporosis.

Normal fluoride requirements

Fluoride, in the proper amount, can cut the level of tooth decay in half and substantially reduce the amount of money spent on dental care. Too much fluoride, especially in children, results in a condition called dental fluorosis. The surface of the teeth becomes discolored by chalky white splotches. This is a cosmetic problem only and does not affect the health of the teeth.

High doses of fluoride can be toxic. Doses between 20–80 mg per day can result in changes in bone that can be crippling, as well as changes in kidney function, and possibly nerve and muscle function. Doses as high as 5–10 g per day can be fatal.

The United States Institute of Medicine (IOM) of the National Academy of Sciences developed values called Dietary Reference Intakes (DRIs) for many vitamins and minerals The DRIs consist of three sets of numbers. The Recommended Dietary.

KEY TERMS

Osteoporosis —A condition found in older individuals in which bones decrease in density and become fragile and more likely to break. It can be exacerbated by lack of vitamin D and/or calcium in the diet.

Allowance (RDA) defines the average daily amount of the nutrient needed to meet the health needs of 97-98% of the population. The Adequate Intake (AI) is an estimate set when there is not enough information to determine an RDA. The Tolerable Upper Intake Level (UL) is the average maximum amount that can be taken daily without risking negative side effects. The DRIs are calculated for children, adult men, adult women, pregnant women, and breastfeeding women. Similar recommendations have been defined elsewhere, e.g., Canada, the United Kingdom, and other European countries.

Fluoride is not considered an essential nutrient so the IOM has not set RDAs for it. Instead, it has set AI and UL levels for all age groups. The daily AIs and ULs for fluoride for healthy individuals as established by the IOM are:

• Children birth-6 months: AI 0.01 mg; UL 0.7 mg
• Children 7-12 months: AI 0.5 mg; UL 0.9 mg
• Children 1-3 years: RDA 0.7 mg; UL 1.2 mg
• Children 4-8 years: RDA 1.0 mg; UL 2.2 mg
• Children 9-13 years: RDA 2.0 mg; UL 10 mg
• Adolescents 14-18 years: RDA 3.0 mg; UL 10 mg
• Men age 19 and older: RDA 4.0 mg; UL 10 mg
• Women age 19 and older: RDA 3.0 mg; UL 10 mg
• Pregnant women of all ages: 3.0 RDA mg; 10 UL mg
• Breastfeeding women of all ages: 3.0 RDA mg; 10 mg

Sources of fluoride in diet

The overwhelming source of fluoride for most people is water. In 1945, Grand Rapids, Michigan, was the first city to add fluoride to its public water supply. About two-thirds of Americans now drink fluoridated water. From the 1950s to the 1970s, the issue of fluoridating public water supplies caused heated debate. Some scientists claimed that fluoridation caused birth defects, cancer, and liver disease. Multiple independent, well-designed studies have conclusively demonstrated that this is false. Fluoridation of water at a level that prevents tooth decay does not increase health risks.

Critics of fluoridation still persist. Some reject existing scientific research and claim that fluoridation is ineffective and/or harmful. For others, fluoridation of public water raises moral issues about personal rights versus the government’s rights. The decision to fluoridate drinking water has generally rested with local governments and communities. The recommended rate of fluoride in water is between 0.7 and 1.2 parts per million (ppm). The fluoridation rate is usually at the low end of the range in warm places and at the high end of the range in cold places because people drink more water and thus get more fluoride where it is warm.

A few foods contain significant amounts of fluoride. Since it is found in seawater, ocean fish contain fluoride. It is also concentrated in tea leaves. The approximate fluoride content for some common foods:

• Tea, 3.5 ounces (100 mL): 0.1-0.6 mg
• Canned sardines with bones, 3.5 oz (100 g): 0.2-0.4mg
• Fish without bones, 3.5 oz (100 g): 0.01-0.17 mg
• Chicken, 3.5 oz (100 g): 0.06-0.10 mg

Toothpaste and mouthwashes containing fluoride provide significant protection against tooth decay. For children who do not drink fluoridated water, the American Dental Association (ADA) and the American Academy of Pediatrics recommend prescription fluoride supplements from age six months onward. Supplements come as liquids and chewable tablets of varying strengths and are prescribed by a pediatrician, family physician, or dentist. In addition, dentists may apply fluoride pastes or varnishes directly to children’s teeth for additional protection. This is usually done at six-month intervals at regular dental check-ups.

Precautions

The amount of fluoride occurring naturally in drinking water varies widely depending on location. People who use wells should have them tested for fluoride. People on public water supplies should call their local public health office to determine if their water is fluoridated. People who primarily use bottled water should consult their supplier about whether or not it contains fluoride. Some built-in home water softening systems may remove fluoride from water. Consult the manufacturer or installer for specific information.

Interactions

Antacids containing aluminum hydroxide and calcium supplements can decrease the absorption of fluoride from the small intestine.

Complications

No complications are expected for people who get daily doses of fluoride falling between the AI and UL limits.

Too little fluoride results in increased tooth decay. Too much fluoride can cause illness or death. A 40 lb (18 kg) child would likely begin to show symptoms of fluoride poisoning after consuming about 55 mg of fluoride (3 mg/ kg of body weight), and a dose of 290 mg (16 mg/kg of body weight) would likely be fatal. In 2004, the American Association of Poison Control Centers reported 24,180 incidents involving toothpaste with fluoride, 440 of which required emergency room treatment. About 22,000 of these incidents were with children under age six who ate toothpaste. Symptoms of fluoride poisoning include nausea, vomiting, diarrhea, headaches, muscle spasms, irregular heart beat, coma, and death. Besides toothpaste and mouthwash, fluoride is also found in pesticides, rodent poisons, and chrome polish for automobiles.

Parental concerns

Children should be taught not to eat toothpaste, and an adult should supervise tooth brushing for children under age six. Mouthwash containing fluoride and prescription fluoride supplements should be kept out of reach of children. A child who eats fluoridated toothpaste or mouthwash should receive an immediate medical evaluation.

Resources

BOOKS

Bryson, Christopher. The Fluoride Deception. New York: Seven Stories Press, 2006.

Fawell, J., K. Bailey, and J. Chilton, eds. Fluoride in Drinking-water. Seattle, WA: IWA Publishing, 2006.

Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. Washington, DC: National Academies Press, 2006.

PERIODICALS

Centers for Disease Control. “Achievements in Public Health, 1900–1999: Fluoridation of Drinking Water to Prevent Dental Caries.”Morbidity and Mortality Weekly Review. 48 (October 22, 1999): 933-40. [cited May 7, 2007]. <http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4841a1.htm>.

Centers for Disease Control. “Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States.” Mortality and Morbidity Weekly Review. 50, RR-14, (Aug 17, 2001): 1-42.

Palmer, Carole, A., and John J. B. Anderson. “The Impact of Fluoride on Health.” American Dietetic Association Reports. 105, no. 10 (October 2005): 1620-1628. [cited May 7, 2007]. http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/home_3795_ENU_HTML.htm>.

ORGANIZATIONS

American Academy of Pediatric Dentistry. 211 East Chicago Ave., Suite 700, Chicago, IL 60611-2616.Telephone: (312) 337-2169. Fax: Fax (312) 337-6329.Website: http://www.aapd.org>.

American Dental Association. 211 East Chicago Avenue,Chicago, IL 60611-2678. Telephone: (312)-440-2500.Website: http://www.ada.org>.

American Dietetic Association. 120 South Riverside Plaza,Suite 2000, Chicago, Illinois 60606-6995. Telephone:(800) 877-1600. Website: http://www.eatright.org>.

Safe Drinking Water Coalition. P.O. Box 443, Lehi, UT 84043. Telephone: (801) 766-8825 or (801) 765-1995. Fax: (801) 776-8826 or (801) 492-0210. Website:http://www.stopfluoridation.homestead.com>.

OTHER

A.D.A.M. “Fluoride in Diet.” MedlinePlus March 3, 2007.[cited May 8, 2007]. http://www.nlm.nih.gov/medlineplus/ency/article/002420.htm>.

“Fluoride.” Oral Health. University of Maryland Medical Center, 2006. [cited May 7, 2007]. http://www.ummedu/oralhealth/flouride.htm>.

Higdon, Jane. “Fluoride.” Micronutrient Information Center Linus Pauling Institute, Oregon State University. April 11, 2003. [cited May 7, 2007]. http://lpi.oregonstate.edu/infocenter/minerals/fluoride>.

Nochimson,Geoffrey.“Toxicity,Fluoride.”eMedicine January 8,2007. [cited May 8, 2007]. http://www.emedicine.com/emerg/topic181.htm>.

Tish Davidson, A.M.

Toothpaste

Background

Toothpaste has a history that stretches back nearly 4,000 years. Until the mid-nineteenth century, abrasives used to clean teeth did not resemble modern toothpastes. People were primarily concerned with cleaning stains from their teeth and used harsh, sometimes toxic ingredients to meet that goal. Ancient Egyptians used a mixture of green lead, verdigris (the green crust that forms on certain metals like copper or brass when exposed to salt water or air), and incense. Ground fish bones were used by the early Chinese.

In the Middle Ages, fine sand and pumice were the primary ingredients in teeth-cleaning formulas used by Arabs. Arabs realized that using such harsh abrasives harmed the enamel of the teeth. Concurrently, however, Europeans used strong acids to lift stains. In western cultures, similarly corrosive mixtures were widely used until the twentieth century. Table salt was also used to clean teeth.

In 1850, Dr. Washington Wentworth Sheffield, a dental surgeon and chemist, invented the first toothpaste. He was 23 years old and lived in New London, Connecticut. Dr. Sheffield had been using his invention, which he called Creme Dentifrice, in his private practice. The positive response of his patients encouraged him to market the paste. He constructed a laboratory to improve his invention and a small factory to manufacture it.

Modern toothpaste was invented to aid in the removal foreign particles and food substances, as well as clean the teeth. When originally marketed to consumers, toothpaste was packaged in jars. Chalk was commonly used as the abrasive in the early part of the twentieth century.

Sheffield Labs claims it was the first company to put toothpaste in tubes. Washington Wentworth Sheffield's son, Lucius, studied in Paris, France, in the late nineteenth century. Lucius noticed the collapsible metal tubes being used for paints. He thought putting the jar-packaged dentifrice in these tubes would be a good idea. Needless to say, it was adopted for toothpaste, as well as other pharmaceutical uses. The Colgate-Palmolive Company also asserts that it sold the first toothpaste in a collapsible tube in 1896. The product was called Colgate Ribbon Dental Creme. In 1934, in the United States, toothpaste standards were developed by the American Dental Association's Council on Dental Therapeutics. They rated products on the following scale: Accepted, Unaccepted, or Provisionally Accepted.

The next big milestone in toothpaste development happened in the mid-twentieth century (1940-60, depending on source). After studies proving fluoride aided in protection from tooth decay, many toothpastes were reformulated to include sodium fluoride. Fluoride's effectiveness was not universally accepted. Some consumers wanted fluoride-free toothpaste, as well as artificial sweetener-free toothpaste. The most commonly used artificial sweetener is saccharin. The amount of saccharin used in toothpaste is minuscule. Companies like Tom's of Maine responded to this demand by manufacturing both fluoridated and non-fluoridated toothpastes, and toothpastes without artificial sweetening.

Many of the innovations in toothpaste after the fluoride breakthrough involved the addition of ingredients with "special" abilities to toothpastes and toothpaste packaging. In the 1980s, tartar control became the buzz word in the dentifrice industry. Tarter control toothpastes claimed they could control tartar build-up around teeth. In the 1990s, toothpaste for sensitive teeth was introduced. Bicarbonate of soda and other ingredients were also added in the 1990s with claims of aiding in tartar removal and promoting healthy gums. Some of these benefits have been largely debated and have not been officially corroborated.

Packaging toothpaste in pumps and stand-up tubes was introduced during the 1980s and marketed as a neater alternative to the collapsible tube. In 1984, the Colgate pump was introduced nationally, and in the 1990s, stand-up tubes spread throughout the industry, though the collapsible tubes are still available.

Raw Materials

Every toothpaste contains the following ingredients: binders, abrasives, sudsers, humectants, flavors (unique additives), sweeteners, fluorides, tooth whiteners, a preservative, and water. Binders thicken toothpastes. They prevent separation of the solid and liquid components, especially during storage. They also affect the speed and volume of foam production, the rate of flavor release and product dispersal, the appearance of the toothpaste ribbon on the toothbrush, and the rinsibility from the toothbrush. Some binders are karaya gum, bentonite, sodium alginate, methylcellulose, carrageenan, and magnesium aluminum silicate.

Abrasives scrub the outside of the teeth to get rid of plaque and loosen particles on teeth. Abrasives also contribute to the degree of opacity of the paste or gel. Abrasives may affect the paste's consistency, cost, and taste. Some abrasives are more harsh than others, sometimes resulting in unnecessary damage to the tooth enamel.

The most commonly used abrasives are hydrated silica (softened silica), calcium carbonate (also known as chalk), and sodium bicarbonate (baking soda). Other abrasives include dibasic calcium phosphate, calcium sulfate, tricalcium phosphate, and sodium metaphosphate hydrated alumina. Each abrasive also has slightly different cleaning properties, and a combination of them might be used in the final product.

Sudsers, also known as foaming agents, are surfactants. They lower the surface tension of water so that bubbles are formed. Multiple bubbles together make foam. Sudsers help in removing particles from teeth. Sudsers are usually a combination of an organic alcohol or a fatty acid with an alkali metal. Common sudsers are sodium lauryl sulfate, sodium lauryl sulfoacetate, dioctyl sodium sulfosuccinate, sulfolaurate, sodium lauryl sarcosinate, sodium stearyl fumarate, and sodium stearyl lactate.

Humectants retain water to maintain the paste in toothpaste. Humectants keep the solid and liquid phases of toothpaste together. They also can add a coolness and/or sweetness to the toothpaste; this makes toothpaste feel pleasant in the mouth when used. Most toothpastes use sorbitol or glycerin as humectants. Propylene glycol can also be used as a humecant.

Toothpastes have flavors to make them more palatable. Mint is the most common flavor used because it imparts a feeling of freshness. This feeling of freshness is the result of long term conditioning by the toothpaste industry. The American public associates mint with freshness. There may be a basis for this in fact; mint flavors contain oils that volatize in the mouth's warm environment. This volatizing action imparts a cooling sensation in the mouth. The most common toothpaste flavors are spearmint, peppermint, wintergreen, and cinnamon. Some of the more exotic toothpaste flavors include bourbon, rye, anise, clove, caraway, coriander, eucalyptus, nutmeg, and thyme.

In addition to flavors, toothpastes contain sweeteners to make it pleasant to the palate because of humecants. The most commonly used humectants (sorbitol and glycerin) have a sweetness level about 60% of table sugar. They require an artificial flavor to make the toothpaste palatable. Saccharin is the most common sweetener used, though some toothpastes contain ammoniated diglyzzherizins and/or aspartame.

Fluorides reduce decay by increasing the strength of teeth. Sodium fluoride is the most commonly used fluoride. Sodium perborate is used as a tooth whitening ingredient. Most toothpastes contain the preservative p-hydrozybenzoate. Water is also used for dilution purposes.

The Manufacturing
Process

Weighing and mixing

• 1 After transporting the raw materials into the factory, the ingredients are both manually and mechanically weighed. This ensures accuracy in the ingredients' proportions. Then the ingredients are mixed together. Usually, the glycerin-water mixture is done first.
• 2 All the ingredients are mixed together in the mixing vat. The temperature and humidity of vat are watched closely. This is important to ensuring that the mix comes together correctly. A commonly used vat in the toothpaste industry mixes a batch that is the equivalent of 10,000 four-ounce (118 ml) tubes.

Filling the tubes

• 3 Before tubes are filled with toothpaste, the tube itself passes under a blower and a vacuum to ensure cleanliness. Dust and particles are blown out in this step. The tube is capped, and the opposite end is opened so the filling machine can load the paste.
• 4 After the ingredients are mixed together, the tubes are filled by the filling machine. To make sure the tube is aligned correctly, an optical device rotates the tube. Then the tube is filled by a descending pump. After it is filled, the end is sealed (or crimped) closed. The tube also gets a code stamped on it indicating where and when it was manufactured.

Packaging and shipment

• 5 After tubes are filled, they are inserted into open paperboard boxes. Some companies do this by hand.
• 6 The boxes are cased and shipped to warehouses and stores.

Quality Control

Each batch of ingredients is tested for quality as it is brought into the factory. The testing lab also checks samples of final product.

Where to Learn More

Books

Garfield, Sydney. Teeth Teeth Teeth. Simon and Schuster, 1969.

Other

Colgate-Palmolive. 1996. http://www.colgate.com/(July 9, 1997).

Crest web site. 1996. http://www.pg.com/docYourhome/docCrest/directory_map.htm 1 (July 9, 1997).

—AnnettePetrusso

fluoride The ion of the element fluorine. Although it occurs in small amounts in plants and animals, and has effects on the formation of dental enamel and bones, it is not considered to be a dietary essential and no deficiency signs are known.

Drinking water containing about 1 part per million of fluoride protects teeth from decay, and in some areas fluoride is added to drinking water to achieve this level. Naturally, the fluoride content of water ranges between 0.05 and 14 ppm. Effect in preventing caries first observed by a dentist, Frederick Motley, in Colorado Springs, 1916.

Water containing more than about 12 ppm fluoride can lead to chalky white patches on the surface of the teeth, known as mottled enamel. At higher levels there is strong brown mottling of the teeth and inappropriate deposition of fluoride in bones known as fluorosis.