Caries Prevention: The Role of Fluoride in Prophylaxis

How fluoride transforms enamel hydroxyapatite into more acid-resistant fluorapatite, what WHO guidelines say about dosing and age groups, and why topical application is now preferred over systemic administration.

The World Health Organization considers fluoride the most effective method currently available for caries prevention. Its main mechanism of action is chemical in nature: during enamel formation and maturation, fluoride replaces part of the hydroxide ions in hydroxyapatite — the mineral that normally makes up dental enamel — forming fluorapatite, a crystalline structure significantly more resistant to attack by acids produced by bacterial fermentation of plaque.

On an already-erupted tooth, fluoride acts through a second, equally relevant mechanism: remineralization. The early stages of enamel demineralization, caused by acids produced by cariogenic bacteria or by acidic foods and drinks, are to some extent reversible — fluoride present in saliva or applied topically promotes mineral deposition on the already-weakened surface, halting or reversing the process before it becomes a full-blown carious lesion. Added to these two mechanisms is a direct antibacterial action, which reduces the adhesion of Streptococcus mutans — the main cariogenic bacterium — to oral tissues.

WHO guidelines on home fluoride prophylaxis indicate precise concentration ranges tied to age: from 6 months to 6 years, a toothpaste with at least 1000 ppm fluoride is recommended, applied twice daily always under adult supervision (to limit the risk of ingestion), while from age 6 onward the concentration can be maintained or increased according to professional guidance. The goal of correct fluoride prophylaxis is always balance: both excess and insufficient fluoride carry risks — fluorosis (an aesthetic alteration of developing enamel) on one hand, and lack of caries protection on the other.

A point on which the scientific community has progressively converged concerns the route of administration: more recent studies show greater effectiveness of topical fluoride administration — toothpastes, gels, professional varnishes — compared to systemic administration (oral supplements), especially in children on already-erupted teeth. In Italy, where drinking water is not fluoridated unlike in other countries, topical application consequently remains by far the most used and recommended method among professionals.

On Oralzon you'll find fluoride gels and varnishes for professional application in the practice, in various concentrations to suit each patient's cariogenic risk profile.