fluoride in the protection of teeth from dental carries

Last edited 03/2022 and last reviewed 10/2023

Fluoride is a natural element that strengthens teeth and prevents their deterioration (1,2,3)

Fluoride in small amounts naturally occurring water sources and it can be found in foods such as meat, fish, eggs and tea

Fluoride prevents tooth decay by making the enamel more resistant to the action of acids

  • in children younger than 6 years fluoride is incorporated into the enamel of permanent teeth, making the teeth more resistant to the action of bacterial and acids from foods

In England, around 10% of the population receives public drinking water served by a fluoridation scheme (4)

  • water fluoridation schemes aim to achieve a level of 1mg of fluoride per litre of water
  • World Health Organization (WHO) guidance recommends a maximum concentration of fluoride in public water supplies of 1.5mg/l, this being protective against any known harmful effect over a lifetime of consumption
    • in the most deprived 20% of areas, the chance of 5 year old children having cavities was 25% lower in areas with a fluoridation scheme than in areas without
    • 5 year olds in areas with higher fluoride concentrations were less likely to experience dental cavities than in areas with low fluoride concentrations
    • up to 56% of hospital admissions for the removal of decayed teeth among children and young people could be prevented in the most deprived areas through water fluoridation scheme

The mechanism of fluoride action

  • the most important action of fluoride is topical, when the fluoride ion is present in the saliva in the appropriate concentration

    • calcium hydroxyapatite is the main mineral responsible for building the permanent tooth enamel after the development of the teeth is finished

    • during tooth growth, the enamel is constantly exposed to numerous demineralization processes, but also remineralization processes
      • presence of fluoride in an acidic environment reduces the dissolution of calcium hydroxyapatite

      • fluoride aids with inhibition of demineralization of enamel, which is carried out through different mechanisms
        • when bacteria metabolize sugars there is a consequent production of lactic acid which reduces the pH in saliva
          • when the pH falls below the critical level of hydroxyapatite (pH 5.5), the process of demineralization of enamel takes place with consequent formation of carries
        • the presence of fluoride in plaque fluid, it will reduce the demineralization, as it will adsorb into the crystal surface and protect crystals from dissolution
          • however the coating of fluoride is only partial, the uncoated parts of the crystal will undergo dissolution on certain parts of the tooth, if the pH falls below level 5.5
          • when the pH increases above the critical level of 5.5, the increased level of fluoride ion leads to remineralization, because it absorbs itself into the enamel and forms fluorhydroxyapatite (1)
        • after repeated cycles of demineralization and remineralization, the outer parts of enamel may change and become more resistant to the acidic environment due to a lowered critical pH level of newly formed crystals (pH 4.5) (1)
        • fluoride ion can also affect the physiology of microbial cells, which can indirectly affect demineralization

Fluoride toothpaste (3)

Toothpastes containing 1,350 to 1,500ppm fluoride are the most effective

  • children under 3 years old should brush twice daily, with a smear of toothpaste containing at least 1,000ppm fluoride
  • children between 3 and 6 years old should brush at least twice daily with a pea-sized amount of toothpaste containing more than 1,000ppm fluoride
  • adults should brush at least twice daily with a toothpaste containing 1,350-1,500ppm fluoride

Reference:

Related pages:

fluoride

dental fluorosis