Fluorides insights in how they work
Professor Adrian Lussi
Head of the Department of Preventive, Restorative and Paediatric Dentistry, University of Bern, SWZ
The onset of caries is characterised by only microscopically visible surface demineralisation on dental hard tissues. Changes of diet and/or oral hygiene habits in combination with optimal fluoridation may stop the progression of a lesion and even allow its remineralisation. The aim of modern dentistry must be a preventive approach rather than invasive repair of the disease. In this context fluoride has an exceptional position. The role of fluoride in caries prevention represents one of the most successful stories in public health. However, the exact mode of action was not well understood for years and still today there are open questions. This lecture has dealt with the mode of action and its implication for daily practice.
Key messages from the lecture
- Fluoride from toothpastes, rinsing solution etc ...may be adsorbed onto or even incorporated into enamel.
- Fluorapatite has approx. 35000 ppm F-, the surface of enamel has only 1000ppm F.
- Due to the solubility characteristics of enamel, demineralization starts at pH 5.5
- This can be improved by incorporating fluoride; fluor(hydroxyl)apatite lowers the solubility and results in a demineralization pH of about 4.5
- In the presence of fluoride, remineralization of enamel leads to increased fluorapatite on the surface and therefore make enamel structure more resistant
- Do not drill white spot lesions, as these are highly remineralized structures and can be stable over years!
- Fluoride enhances remineralization by lowering the critical pH over which remineralization still can occur
- At low pH, fluoride forms a CaF2 layer on the tooth?s surface which protects enamel from demineralization
- This CaF2 depot will be released upon acid attack and fluoride may afterwards be incorporated into demineralized enamel or may enhance remineralization
- Biannual application of fluoride varnish such as Duraphat significantly reduces caries experience in children (mean age 2 years) (Weintraub et al. 2006)
- Fluoride inhibits the enolase activity within plaque bacteria and therefore reduces the microbes metabolism which leads to a reduced acid production
- The fluoride?s mode of action consists of three activities: Inhibition of demineralization, promotion of remineralization and inhibition of plaque metabolism
