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Fluoride
Description:
Fluoride is most concentrated within tissues such as cementum, bone, dentin, and enamel. Fluoride is the ionic form of fluorine, and is instrumental in protecting bone and tooth enamel from loss of constituent minerals.
Fluoridated water is the most abundant and important source of fluoride for humans, and has been proven to aid in the reduced incidence of dental caries.
Excessive fluoridation of teeth has resulted in a condition called mottle enamel, which is characterized by discolored enamel. Extremely high fluoride intake has been known to result in death.
Inconclusive evidence has linked fluoride to such phenomena as enhanced iron absorption and increased wound-healing rate.
Method of Action:
Fluoride is proposed to enhance the precipitation of hydroxyapatite crystals in solutions of calcium and phosphate (e.g., blood) and therefore tends to prevent the demineralization of bone and teeth.
It has been further proposed that fluoride becomes integrated within the hydroxyapatite crystals, creating enlarge and less soluble crystals. Because these crystals are less soluble and less reactive, dissolution of the tooth structure by acidic by-products of microorganism metabolism cannot occur as readily. Bone is also less likely to demineralize due to the decreased solubility of the fluoride containing crystals.
The action of fluoride on hydroxyapatite crystals in bone and teeth make it a probable aid in the prevention of dental caries and various bone demineralization disorders, such as osteoporosis, osteomalacia, and periodontal disease.
Plasma fluoride levels stay relatively constant, even in times of low fluoride consumption, due to the availability of fluoride from bones. Fluoride absorption is very efficient and occurs primarily in the stomach. Fluoride treatments for teeth are most effective if the fluoride comes into direct contact with the teeth, as is the case with fluoridated water and toothpaste.
Excretion occurs primarily through the urine and sweat.
Properties & Uses:
Fluoride intake throughout life has been cited as beneficial in reducing the prevalence of senile osteoporosis. High levels of fluoride intake have been used therapeutically in the treatment of osteoporosis.
Water fluoride concentrations of one part per million have resulted in a decrease in the incidence of dental caries of up to 70%, as well as large decreases in the incidence of periodontal disease.
Although it has not been proven conclusively, fluoride may increase the rate of wound healing and enhance iron absorption.
Toxicity Levels:
Fluoride can be toxic, but only in amounts far in excess of normal dietary consumption. One part per million fluoride (or one milligram per liter of water) is added to fluoridated water supplies. Concentrations of two to eight parts per million may result in mottle enamel, or dental fluorosis. These disorders result in a discoloration of enamel. Concentrations of 8 to 20 parts per million can result in osteosclerosis. At concentration of 2,500 times the recommended daily allowance death can occur.
Acute fluoride toxicity is very rare, with less than 500 cases recorded up to 1970. Mottled tooth enamel occurs in some areas with excess fluoride added to water supplies, but the problem is only aesthetic in nature. Prolonged excess fluoride exposure (more than 20 milligrams daily for 20 or more years) can lead to crippling skeletal fluorosis, but this is extremely rare.
Under experimental conditions, high levels of fluoride have been associated with higher calcium retention and interference of collagen formation, with possible inhibition of normal growth.
Recommended Dietary Allowances:
RDA for adults 1.5 - 4.0 mg
RDA for child/adolescent 1.5 - 4.0 mg
RDA for age 1 3 0.5 - 1.5 mg
RDA for age 0 1 0.1 - 1.0 mg
Food Sources:
Buckwheat Fish Fluoridated water
Lettuce Spinach Rice
Red Wine Coffee White wine
Soybeans Tea (black) Onions