FLUORIDE MECHANISM

FLUORIDE
Fluoride ions promote the formation of fluorapatite in enamel in the presence of calcium and phosphate ions produced during enamel demineralization by plaque bacterial organic acids.

Fluoride ions can also drive the remineralization of previouslydemineralized enamel if enough salivary or plaque calcium and phosphate ions are available.

availability of calcium and phosphate ions can be the limiting factor for net enamel remineralization to occur

this is highly exacerbated under xerostomic condition.

FLUORAPATITE

when the fluoride is applied, for every two fluoride ions, 10 calcium ions and six phosphate ions are required toform one unit cell of fluorapatite (Ca10(PO4)6F2)..

Fluoride mechanisms

1) Free fluoride ion combines with H+ to produce hydrogen fluoride, which migrates throughout acidified plaque.

This ionized form is lipophilic and can readily penetrate bacterial membranes.

Bacterial cytoplasm is relatively alkaline, which forces the dissociation of H+ and F-.

Fluoride ion inhibits various cellular enzymes (enolase, proton extruding ATPase)key to sugar metabolism.

Hydrogen ions simultaneously acidify the cytoplasm, thus slowing cellular activities and inhibiting bacterial function


2) Fluoride integrated in the enamel surface (as fluorapatite, FAP) makes enamel more resistant to demineralization than HAP during acid challenge.

FLUORAPATITE formed is less soluble,this is due to incorporation of fluoride and carbonate is washed out (Tencate).



3) Fluoridated saliva not only decreases critical pH, but also further inhibits demineralization of the deposited CaF2 at the tooth surface.

DCNA,1999
Australian Dental Journal,2008