Overview

Fluoride is the anion formed when the element fluorine gains an electron and becomes negatively charged. In chemistry it is written as F− and is distinct from elemental fluorine (F2), a highly reactive gas. Fluoride occurs naturally in minerals, soils and water and is present in low concentrations in many foods. Its most familiar application is in dentistry, where fluoride compounds are used to reduce the risk of tooth decay.

Chemistry and common forms

As an ion, fluoride combines with various cations to form salts and compounds. Common examples include:

  • Sodium fluoride and sodium fluorosilicate, used in some water fluoridation programs and industrial processes.
  • Stannous fluoride and sodium monofluorophosphate, used in some toothpastes and topical dental products.
  • Fluorapatite, a naturally occurring mineral in bones and teeth when fluoride replaces hydroxide in hydroxyapatite.

For more technical descriptions see chemical references and general element profiles at element resources.

Uses and importance

Fluoride is widely used to strengthen tooth enamel and reduce dental cavities. It can be applied topically through toothpaste and mouth rinses, or delivered systemically by adding controlled amounts to community water supplies — a practice known as fluoridation. Professional dental treatments may use concentrated fluoride varnishes or gels for people at higher risk of decay. Fluoride compounds also appear in industrial uses, such as aluminum production and certain manufacturing processes.

At appropriate concentrations fluoride helps remineralize enamel and inhibits the activity of cavity-causing bacteria. Public health guidelines recommend modest concentrations for community water supplies; recommended target levels vary by country and may be adapted for climate and local fluoride exposure. Excessive fluoride intake over time can lead to dental fluorosis (changes in tooth enamel) or, in very high exposures, skeletal effects. Regulatory and health authorities provide guidance on safe use; see public health resources at health agency and practice guidance at dental associations.

History and controversies

Interest in fluoride and dental health expanded during the 20th century after observational studies linked natural fluoride in drinking water to lower rates of cavities. The introduction of water fluoridation programs prompted public debate over individual consent, perceived risks and benefits, and environmental impacts. Discussions continue in many communities; balanced overviews and policy statements are available from scientific bodies and local health authorities at policy sources, research reviews and public information portals information pages.

Understanding fluoride requires distinguishing the ion (F−) from elemental fluorine and from the many compounds in which the ion appears. When used in recommended amounts, fluoride is an effective and inexpensive tool for reducing dental decay, but like any chemical it requires appropriate management and monitoring to minimize adverse effects.