[Mechanism of action of fluorides in local/topical application]

The marked caries reduction in many countries over the last two decades is thought to be mainly the result of the widespread and frequent use of low concentrations of fluorides mainly via toothpastes. This article gives a review on fluoride sources in the oral cavity and discusses the physiochemical mechanisms by which fluoride interacts with enamel during the caries process and its reversal. From this review it becomes clear that fluoride incorporated into the enamel mineral during tooth development has little effect on the caries process. It is the fluoride incorporated posteruptively and in the aqueous phase during the caries challenge that is of primary importance. The most effective caries preventive fluoride regimen, both from a theoretical perspective and as proved clinically, is the frequent (daily) low concentration application of fluoride from toothpastes and/or mouthrinses. High concentrations, however, used at intervals of months or years and administered by the dentist, work initially not only on both de- and remineralisation, but also by providing fluoride as calcium-fluoride or absorbed in early lesions which is subsequently available over prolonged periods.