Teeth are composed of a substance called hydroxyapatite, mostly made up of calcium (Ca), phosphate (PO4) and hydroxide (OH–), as well as carbonate and water. Want to find out more about the structure of your teeth? Click here.
- Fluoride can replace some of the hydroxide and carbonate, so the enamel surface is now partially made of a substance called fluorapatite
- Fluorapatite is more resistant to acid, for instance, the ‘critical pH’ where acid erosion can take place is pH 5.5 for hydroxyapatite but pH 4.5 for fluorapatite
- However, this is not the main reason fluoride can protect against acid erosion
Fluoride can also bind with calcium in saliva to form a calcium-fluoride (CaF2) layer over enamel and in erosion pits
Fluoride (and calcium-fluoride) can stay in saliva and in the pellicle (the layer of saliva coating the teeth). Learn more about Saliva and your teeth here.
This can help protect against erosion by preventing hydroxyapatite crystals from dissolving (‘demineralisation’) and speeding up the re-building of the crystals (‘remineralisation’)
Fluoride in toothpaste or fluoride mouthrinses can attach to the gum, the pellicle and plaque. It is then slowly released over a number of hours and can speed up the rebuilding of teeth (‘remineralisation’) at a lower pH of 4.5 than if it isn’t present, where the pH needs to be above 5.5 for remineralisation to take place. Find out more about how acid affects your teeth here.
Fluoride in toothpaste or fluoride mouthrinses may be combined with a mineral to make it more effective against erosion. Sodium fluoride (NaF), amine fluoride (AmF), stannous (tin) fluoride (SnF2)
Vogel GL. Oral Fluoride Reservoirs and the Prevention of Dental Caries. In: Buzalaf MAR (ed): Fluoride and the Oral Environment. Monogr Oral Sci. Basel, Karger, 2011, vol 22, pp 146–157.
Magalhães AC, Wiegand A, Rios D, Buzalaf MAR, Lussi A. Fluoride in Dental Erosion. In: Buzalaf MAR (ed): Fluoride and the Oral Environment. Monogr Oral Sci. Basel, Karger, 2011, vol 22, pp 158–170.
Buzalaf MAR, Pessan JP, Honório HM, ten Cate JM. Mechanisms of Action of Fluoride for Caries Control Buzalaf MAR (ed): Fluoride and the Oral Environment. Monogr Oral Sci. Basel, Karger, 2011, vol 22, pp 97–114