Merck Manual

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Fluorine Toxicity


Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Reviewed/Revised Dec 2021 | Modified Sep 2022
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Most of the body’s fluorine (F) is contained in bones and teeth. Fluoride (the ionic form of fluorine) is widely distributed in nature. The main source of fluoride is fluoridated drinking water.

Excess fluorine can accumulate in teeth and bones, causing fluorosis. Drinking water containing > 10 parts per million is a common cause. Permanent teeth that develop during high fluoride intake are most likely to be affected. Exposure must be much greater to affect deciduous teeth.

The earliest signs of fluorine toxicity are

  • Chalky-white, irregularly distributed patches on the surface of the enamel

These patches become stained yellow or brown, producing a characteristic mottled appearance. Severe toxicity weakens the enamel, pitting its surface. Bony changes, including osteosclerosis, exostoses of the spine, and genu valgum, can develop but only in adults after prolonged high intake of fluoride.

No tests to diagnose toxicity are available.

Treatment of fluorine toxicity involves reducing fluoride intake; eg, in areas with high fluoride water levels, patients should not drink fluoridated water or take fluoride supplements. Children should always be told not to swallow fluoridated toothpastes.

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NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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