Fluorosis is caused by excessive exposure to fluoride. The primary source of excess fluoride ingestion is drinking-water with high fluoride concentrations. According to the World Health Organization, fluoride concentrations in drinking-water should not exceed 1.5 mg/l (1.5 ppm). Secondary sources of fluoride exposure include fluoride-rich beverages, foodstuffs and dental products. Excess fluoride intake manifests itself primarily in disrupted tooth enamel formation (dental fluorosis) and bone damage (skeletal fluorosis). The two classification systems widely used for grading the severity of dental fluorosis are the Dean’s Index and the Thylstrup-Fejerskov Index. To estimate the scale of dental fluorosis as a global public health problem, a literature search was conducted in the PubMed database with ‘fluorosis’ as a search term, as well as in publications available in print. The search yielded a number of studies describing the problem of dental fluorosis in countries such as Mexico (100% prevalence), Sri Lanka (72.9%), India (64.3%), the USA (61.3%) and Brazil (from 39.6 to 58.9%). High fluoride drinking-water concentrations influenced the prevalence of dental fluorosis. With the mean concentration of 1.58 ppm, as many as 72.9% of the study population had dental fluorosis (Sri Lanka). Higher fluoride concentrations were correlated with a higher prevalence of more severe manifestations of the disease: the proportion of population affected with stage 6 or 7 (severe) fluorosis was 4.4% at 2.5 ppm and 20.6% at 5.1 ppm (Mexico). In the regions of the world with high fluoride drinking-water concentrations, steps should be taken to prevent dental fluorosis.

Key words: dental fluorosis, drinking-water, oral health, prevalence.