Enamel protection
Research shows that the primary mode of action of fluoride in the protection against caries is by a topical effect, where it can adsorb onto the outer tooth enamel layer. This will increase its strength and resistance to attack from acids in the mouth and promote remineralization. This is due to fluoride becoming incorporated into the crystal lattice structure of the tooth, which makes it less soluble in acid and, therefore, confers resistance to attack.
To view animations depicting these processes click here.
Differences in fluoride toothpastes
However, not all fluoride toothpastes are the same. Even formulations containing similar levels of fluoride can vary in effectiveness. Factors such as formulation pH are important and exclusion of ingredients that contain by design, or by impurities, chemical species such as divalent cations can increase the levels of available fluoride in toothpaste. The presence of ingredients such as orthophosphate can partially inhibit fluoride uptake. [Regatati, 1970; Friberfer, 1975; Newby, 2006; Newby, 2007] The benefits conferred by the toothpaste are influenced by the amount of fluoride released into the saliva and adsorbed by the enamel. Sodium fluoride (NaF) has been shown to be slightly more effective (5–10%) than monofluorophosphate (MFP) when incorporated into an equivalent toothpaste base, possibly because the latter requires activation by a salivary enzyme to release free fluoride. [Stookey et al, 1993]
