Dr. Shilpy Bhandari 13 Jul 2021

Fluoride is a naturally-occurring mineral essential for our body. It is found in water, soil, plants, rocks, and even air. It helps in the maintenance of bones and teeth. It is effective in preventing tooth decay (cavities) in children and adults. Since tooth decay is a major health problem, several measures are adopted at community and individual levels to provide individuals with sufficient fluoride. However, excess exposure to fluorine can have adverse effects. This article discusses the benefits of fluorides on teeth, the mechanism of action of fluorides, different fluoride delivery methods, and the adverse effects of fluorides.

Benefits of fluoride 

Some of the benefits of fluoride in teeth:

  • Fluoride strengthens the enamel (outermost layer of the tooth) and makes teeth resistant to decay.
  • It reverses the progression of early-stage decay.
  • It helps rebuild the demineralized areas (weakened enamel) of tooth surfaces. 
  • Fluoride inhibits the growth of bacteria in the mouth.
  • It protects teeth from demineralization (loss of minerals) and is recommended in swimmers or individuals who complain of teeth sensitivity.

Mechanism of action of fluoride

Fluoride taken during tooth development (in children) make teeth resistant to tooth decay. Here are some of the ways fluoride controls decay:

  • The fluoride in saliva or plaque (colorless coating on tooth surfaces) delays demineralization and promotes remineralization of initial tooth decay. 
  • It interferes in the process by which decay-producing bacteria ferment sugar to produce cavity-causing acids.
  • Fluoride in the saliva or plaque combines with the mineral content of teeth (calcium and phosphate) to form a compound that makes the tooth stronger and more resistant to decay.
  • In higher concentrations, fluoride has an antibacterial effect on decay-producing bacteria in the mouth.

Sources of fluoride ingestion:

Foods such as milk, tea leaves, grapes, avocado, and fish are good sources of fluoride. However, due to variation in the consumption, fluoride levels in the oral cavity may vary. So, the introduction of additional fluoride prevents tooth decay. These methods include: 

Community-based fluoridation: It is a cost-effective method of delivering fluoride to the community. In the US, community water contains 0.7 parts per million (0.7 milligrams of fluoride ion per liter) of fluoride. According to the United States Centers for Disease Control and Prevention (CDC), 73% of the US population has access to community-based fluoridated water in 2018. Research suggests that water fluoridation has led to a significant reduction in decayed, missing, and filled milk teeth in children.

Application of fluoride gels and varnishes by a dentist: The application of topical gels or varnishes on tooth creates a layer of calcium fluoride on the tooth's enamel surface. Usually, bacteria in the oral cavity ferments the food on the tooth surface and produces acid. This acid reduces the pH of the saliva and causes demineralization of the tooth. On the other hand, when fluoride gel or varnish is applied, it restores the pH of the saliva. As a result, fluoride helps regain the lost minerals of the tooth. Dentists recommend the use of 1.23% of APF (acidulated phosphate fluoride) and 5% NaF (sodium fluoride) gel in children. In children with high risk of decay, gel application is recommended 2-4 times in a year.

Use of toothpaste and mouthwash at home: Daily use of fluoridated toothpaste is effective in oral hygiene maintenance and fluoride supplementation. Fluoride levels in regular toothpaste are between 1000 and 1500 parts per million (ppm). For children below three years of age, no more than rice grain size (0.1mg) of toothpaste with low fluoride levels of 400-550 ppm is recommended. In children between 3-6 years of age, pea-sized (0.25mg) toothpaste is recommended. Children should brush under their parents' guidance as they tend to ingest ~80% of fluoridated toothpaste. Use of 0.09% fluoride mouthwash is also an effective way of increasing fluoride levels in the mouth.

Adverse effects

High fluoride levels in water (above 1.5 ppm) can result in several adverse effects on teeth. Long-term ingestion of high fluoride levels in water can also result in skeletal fluorosis. Some adverse effects of excess fluoride intake are:

  • Enamel fluorosis: Excess fluoride intake during tooth formation stages can lead to enamel fluorosis (change in appearance of the enamel). Consumption of high fluoride in children (1-3 years of age) during tooth development causes fluorosis of permanent incisors (front teeth). However, the risk of enamel fluorosis is limited to children below eight years of age. This is because the maturation of enamel (stage of tooth development) completes by this age. So, it is no more susceptible to fluorosis. 
    • Based on the effect, enamel fluorosis can be divided into three stages:
    • Mild: This form is characterized by less apparent, chalky, lace-like markings on the enamel tooth surface.
    • Moderate: In this form, more than half of the tooth's enamel surface is opaque and chalky white in appearance.
    • Severe: In its severe form, enamel fluorosis may cause brown stains on the tooth surface. The tooth may become brittle with pits on the enamel surface. 
  • Fluoride toxicity: Ingestion of large quantities of fluoride can turn toxic. According to the American Dental Association, no more than 120 mg fluoride or 264 mg sodium fluoride should be used at once. The recommended limit of consumption of fluorine is ~15mg per kg of body weight. Ingestion of more than 250 mg of fluoride at once in infants may result in death. Signs and symptoms of fluoride toxicity include nausea, vomiting, abdominal cramps, pain, fits, irregular heartbeats, and coma.
  • Skeletal fluorosis: It is caused by the accumulation of high fluoride levels within the bone or joints. This leads to bone loss and lowering of calcium levels in the bones. Key symptoms of skeletal fluorosis include chronic joint pain, stiffness of joints, pain, loss of muscle tissue, neurological abnormalities, restricted movements of joints, and ossification of the spine (soft tissue turning into bone, decreasing flexibility).


Fluorides play a major role in the development of teeth, but are harmful in excess quantities. Individuals should use fluorides meticulously to benefit from the anti caries (decay) effect of fluorides, while limiting its harmful effects.

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About the Author:
Dr. Shilpy Bhandari is an experienced dental surgeon, with specialization in periodontics and implantology. She received her graduate and postgraduate education from Rajiv Gandhi University of Health Sciences in India. Besides her private practice, she enjoys writing on medical topics. She is also interested in evidence-based academic writing and has published several articles in international journals.


  • O'Mullane DM, Baez RJ, Jones S, Lennon MA, Petersen PE, Rugg-Gunn AJ, Whelton H, Whitford GM. Fluoride and Oral Health. Community Dent Health. 2016 Jun;33(2):69-99. PMID: 27352462.
  • Hellwig E, Lennon AM. Systemic versus topical fluoride. Caries Res. 2004 May-Jun;38(3):258-62. doi: 10.1159/000077764. PMID: 15153698.
  • Martínez-Mier EA. Fluoride: its metabolism, toxicity, and role in dental health. Journal of Evidence-Based Complementary & Alternative Medicine. 2012 Jan;17(1):28-32.
  • Marinho VC, Higgins JP, Logan S, Sheiham A. Topical fluoride (toothpastes, mouthrinses, gels or varnishes) for preventing dental caries in children and adolescents. Cochrane Database Syst Rev. 2003;2003(4):CD002782. doi: 10.1002/14651858.CD002782.
  • Tenuta LM, Cury JA. Fluoride: its role in dentistry. Braz Oral Res. 2010;24 Suppl 1:9-17.
  • Marinho VC. Evidence-based effectiveness of topical fluorides. Adv Dent Res. 2008 Jul 1;20(1):3-7. doi: 10.1177/154407370802000102.
  • Policy on Use of Fluoride. Pediatr Dent. 2018 Oct 15;40(6):49-50. PMID: 32074848.
  • Faller RV, Noble WH. Protection From Dental Erosion: All Fluorides are Not Equal. Compend Contin Educ Dent. 2018 Mar;39(3):e13-e17.