Employment of fluorides means the employment of methods and processes which aim at increasing the fluoride concentration of the tooth surface. Methods requiring cooperation of experts (dentist, mouth hygienist) mean application of fluoride compounds of higher concentration at given periods (3 to 6 months). Methods not requiring professional cooperation prefer frequent (daily) employment of products of low concentration (toothpastes, mouthwashes etc.). In countries where such fluoride containing oral hygiene products are used extensively and systematically, frequency of caries significantly decreases. By topically employed fluorides the beneficial effect of the systemic fluoride use, (drinking water, salt, tablets) is increased.