Fluoride (Fl)

F – Fluorine is found in igneous rocks at 625 ppm; in shale at 740 ppm; sandstone at 270 ppm; limestone at 330 ppm; fresh water at 0.09 ppm; sea water at 1.3 ppm; soils at 200 m (fluoride can be “fixed ” or tightly bonded in several types of clays. Certain F rich soils in Madras, Spain and South America are toxic to grazing livestock.

Fluorine is found in marine plants at 4.5 ppm; land plants at 0,5 to 40.0 ppm (accumulated by Dichapetolum cymosum); marine animals at 2.0 ppm (accumulates in fish bone); land animals at 150 to 500 ppm in mammalian soft tissues and 1,500 ppm in bone and teeth.

Prior to 1972, fluoride was considered essential in animals because of its apparent benefit for tooth enamel in warding off dental caries (“cavities”). In 1972, Schwarz proved that fluoride was in fact an essential mineral.

The skeletal reserves of fluoride in an adult man reach 2.6 grams; the average daily intake by Americans is 4.4 mg from combined sources of food and water.

Fluoridation of drinking water is still highly controversial – some studies show that fluoridated water helps reduce fractures from osteoporosis while other studies showed an increase in hip fractures. Clinical toxicity is observed as dental fluorosis at fluoride concentrations of 2 to 7 ppm and osteosclerosis at 8 to 20 ppms; chronic systemic toxicity appears when the fluoride levels reach 20 to 80 mg per day for years.

Approximately 10,000 American towns and cities serving 100 million people have added fluoride to their drinking water at the rate of 1 mg /L which has reportedly reduced dental caries by 60 to 70 percent. In certain western states in the United States, there is an excess of fluoride, reaching levels of 10 to 45 ppms with resultant mottling of teeth in children.

As a result of epidemiological studies by Yiamouyiannis and Burk in 1977, full-scale congressional hearings were held to examine the charge that 10,000 excess cancer deaths were caused by fluoridation of certain public water systems. As a result of those hearings, the committee mandated that the U.S. Public Health Service conduct animal studies to confirm or refute the theory that fluoridated water increased cancer deaths. The studies were carried out by the National Toxicology Program under the supervision of the U.S. National Public Health Service with special focus on oral, liver and bone cancers

In 1990, the results of the fluoride study showed an increase in rat precancerous in oral mucus membrane cells; there was an increase in cancers of the oral mucus membranes (squamous cell carcinoma); a rare form of osteosarcoma appeared at double the rate in males as females; and there was an increase in thyroid follicular cell tumors and liver cancer (hepatocholangiocarcinoma).


Fluoride is an essential trace mineral required to build strong bones and teeth. Fluoride is the ionized form of the element fluorine. The estimated safe and adequate daily dietary intake of fluoride for adults is 1.5 to 4 mg. Most research regarding fluoride has focused on the relationship of fluoride to preventing tooth decay because fluoride hardens tooth enamel. Fluoride is absorbed by gums and incorporated into the structure of developing teeth as a fluoride-containing mineral, fluorapatite. This mineral strengthens the enamel and dentine, making them more resistant to bacterial decay. Fluoride is part of BONE structure and fluoride may protect against osteoporosis Traces of fluoride also occur in soft tissues but its role there is unclear.

Adult intake of fluoride in the United States from various sources may reach 0.5 to 1.0 mg daily. Seafood and tea are especially good sources of fluoride. Low levels are present in many foods and in drinking water. Two fluoride-containing compounds, stannous fluoride and sodium fluorophosphate, are common ingredients of toothpaste and mouth rinse. Most toothpastes contain one milligram of fluoride per gram of paste, and a fluoride overdose is possible. Do not swallow fluoridated toothpaste.

Side effects of chronic fluoride overdose include stomach ulcers, stress-induced bone fractures and swollen joints. Questionable evidence for fluoride being a carcinogen in rats was found by the Natural Toxicology Program in 1990. A 1991 review by the U.S. Public Health Service (PHS) concluded that there is no evidence that fluoride causes cancer in humans. The incidence of bone cancer in males below the age of 20 has risen since 1973, but the panel concluded that this is not related to fluoridation. The PHS review recommended further study to determine the relationship between fluoride intake and bone fractures. The National Research Council also concluded that current levels of fluoride in drinking water do not increase the risk of kidney disease, birth defects or intestinal problems.

Li, Y., “”Fluoride: Safety Issues,” Journal of the Indiana Dental Association, 72:3 (May-June 1993), pp. 22-26.

 

Fluorine in the form of fluoride occurs in nature ubiquitously and enters the body as a variable constituent of both drinking waters and foods. The total intake of adults is usually within the range 0.2-2.0 mg of fluoride/day but higher intakes are not uncommon where the fluoride content of drinking water is high. The fluoride content of natural waters may range from less than 0.1 mg/liter to more than 20 mg/liter. In the USA and in Central Europe generally, the fluoride content of natural waters is at the lower end of the range. In Asian countries and in many African countries, levels of fluoride in waters are typically towards the higher limit of the distribution. Some industrial fumes and dusts from chemical or smelting plants contribute significantly to environmental fluoride. The total ingestion of fluoride from all sources is taken into consideration when safe levels are derived. Body fluoride status depends on a multiplicity of factors, including the fluoride content of natural drinking water, the total amount ingested daily, the duration of ingestion and the efficiencies of intestinal absorption and renal excretion. Since rises in environmental temperature increase water consumption, seasonal fluctuations occur in total fluoride ingestion and retention.

Fluoride Biochemical function

The complex and frequently indirect relationships between low fluoride intakes and increased susceptibility to dental caries have been reviewed elsewhere. Fluoride is reported to be required for the transformation of osteocalcium phosphate to apatite, the chief mineral component of skeletal tissue. Higher fluoride contents increase the crystallinity of apatite and decrease its solubility in acid. Although the exact biological roles of fluoride in humans have not been established, animal experiments have suggested that it may be a structurally important constituent of bone collagen and of the glycosamino-glycans of the vascular system, the skin and other tissues. A single study reported by Schwartz & Milne suggested that the growth of young rats was retarded if they were kept on low intakes of dietary fluoride (3-25mcg of fluoride/100 kcal). This growth retardation was reversed by supplementation of the diet with fluoride. Diets low in fluoride content (< 0.3mg of fluoride/kg dry matter) offered to goats during pregnancy and lactation and to the kids during postnatal growth reduced by 16% the 4-year life expectancy of the latter. This effect was not apparent if dietary fluoride was in the range 1.5-2.5 mg/kg.Tissue fluoride

Ingested fluoride accumulates in bone tissue. The fluoride content of human bones varies from 300 to 7000 mcg/g of dry tissue depending on total fluoride exposure. Studies carried out in India suggest that the body fluoride burden of individuals exposed to higher levels of environmental fluoride may be 2-3 times higher than normal, judging from the fluoride content of bone dry matter. Bone fluoride is a good indicator of lifetime exposure of the body to the element that overt clinical signs of fluoride deficiency exist. No specifically diagnostic clinical or biochemical parameters have been related to fluoride inadequacy. The Expert Consultation was therefore unable to specify a minimum desirable intake. However, in view of the toxicity associated with excessive fluoride ingestion from a variety of sources, recommendations for maximum safe intakes are required. For this purpose, dental mottling may be taken as a definitive indication of toxicity.

Fluoride Safe levels

Although fluoride should probably be regarded as essential, there is no evidence so far from human studies that overt clinical signs of fluoride deficiency exist. No specifically diagnostic clinical or biochemical parameters have been related to fluoride inadequacy. The Expert Consultation was therefore unable to specify a minimum desirable intake. However, in view of the toxicity associated with excessive fluoride ingestion from a variety of sources, recommendations for maximum safe intakes are required. For this purpose, dental mottling may be taken as a definitive indication of toxicity.


Key Fluoride Data Sites

Scientific minded people should learn more about fluoride. If you work in the dental field, the following websites should provide you with information that can be used to educate your patients with scientific data that has been documented on the world wide web. Knowing both sides of the issues of fluoride in the 90’s is something good for not only dental technicians, but people employed in water treatment plants, and people who manufacture fluoride products.