Many studies have shown that the application of fluoride reduces dental decay in both children and adults. (American Academy of Pediatric Dentistry: Guideline on fluoride therapy. Pediatr Dent. 33 (special issue), 2011, 153–156.)
Fluoride is commonly found as a negatively charged ion. In this form it can combine with other molecules to create crystals. Our teeth are made of crystals, hydroxyapatite crystals, and cavities form when bacteria in our mouths melt these crystals with acids. Fluoride ions are used to replace the hydroxide ion within the crystals. Fluoroapatite crystals are harder for the bacteria’s acids to melt, thus protecting your teeth from cavities. Constant applications of fluoride ensure that fluoroapatite crystals are present in your tooth making it stronger.