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Topical Fluorides I

Mechanisms of Action of Fluoride

Tooth tissue mineral exists as a carbonated apatite containing calcium, phosphate and hydroxyl ions, making it a hydroxyapatite [Ca₁₀.(PO₄)₆.(OH)₂]. When the pH is below the critical pH for hydroxyapatite (<5.5), demineralisation occurs and when the pH returns to 7.0, remineralisation occurs. Thus there is an equilibrium between demineralisation and remineralisation. When fluoride is present during remineralisation, it forms fluorapatite [Ca₁₀.(PO₄)₆.F₂], which is more stable and resistant to further acid attacks. The proposed mechanisms of action for fluoride are:

• it has an effect during tooth formation making the enamel crystals larger and more stable;
• it inhibits plaque bacteria by blocking the enzyme enolase during glycolysis;
• it inhibits demineralisation when in solution;
• it enhances remineralisation by forming fluorapatite;
• it affects the crown morphology making the pits and fissures shallower and hence less likely to create stagnation areas.

It is the activity of the fluoride ion in the oral fluid that is important in reducing the solubility of the enamel rather than having a high content of fluoride in enamel. Therefore a constant supply of low levels of intra-oral fluoride, particularly at the saliva/plaque/enamel interface, is of most benefit in preventing dental caries.

Fluoride Formulations

• Sodium fluoride (NaF).
• Sodium monofluorophosphate (NaMFP).
• Stannous fluoride (SnF).
• Amine fluoride (AmF).

Fluoride Gels, Rinses and Varnishes

Topical fluorides should be used in children assessed as being at increased risk for caries development, including children with special oral health care needs.

Fluoride Gels

These can be applied in trays or by brush with 26% caries reductions reported. They are high in fluoride (1.23% = 12 300 ppm) for professional use and lower (1000 ppm) for home use. There is a risk of toxicity with the high fluoride containing gels and the following safety recommendations should be followed:

• no more than 2 ml per tray;
• sit patient upright with head inclined forward;
• use a saliva ejector;
• instruct the patient to spit out for 30 seconds after the procedure;
• do not use for children under 6 years of age.

Clinical Characteristics

• Long contact time.
• High fluoride concentrations.
• Long intervals between applications.
• Professional application and prescription from a dentist required.

Fluoride Rinses

These can be either daily rinses containing 0.05% (225 ppm) or weekly rinses 0.20% (900 ppm) of sodium fluoride. Advise patients to use their/>

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