a lot of fluoride-containing water in combination with other fluoride sources, such as swallowing fluoridated toothpaste, consuming food with a high fluoride content, or consuming fluoride supplements. the use of fluoride supplements as a prevention for tooth decay is rare in areas with water fluoridation, but was recommended by many dentists in the uk until the early 1990s. in november 2006 the american dental association published information stating that water fluoridation is safe, effective and healthy; that enamel fluorosis, usually mild and difficult for anyone except a dental health care professional to see, can result from ingesting more than optimal amounts of fluoride in early childhood; that it is safe to use fluoridated water to mix infant formula; and that the probability of babies developing fluorosis can be reduced by using ready-to-feed infant formula or using water that is either free of fluoride or low in fluoride to prepare powdered or liquid concentrate formula. they go on to say that the way to get the benefits of fluoride but minimize the risk of fluorosis for a child is to get the right amount of fluoride, not too much and not too little. "your dentist, pediatrician or family physician can help you determine how to optimize your child's fluoride intake." prevention dental fluorosis can be prevented by lowering the amount of fluoride intake to below the tolerable upper limit. this can be achieved by consuming de-fluorinated water and improving the general nutritional status of the people. history in ancient times, galen describes what is thought to be dental fluorosis. however, it was not until the early 20th century that dental fluorosis became increasingly recognized and scientifically studied. in 1901 eager published the first description of the "mottled enamel" of immigrants from a small village near naples, italy. he writes that the condition is called "denti di chiaie" (chiaie teeth), named after stefano chiaie, an italian professor. in the united states of america, a dentist, frederick mckay, set up practice in colorado springs in 1901 and discovered a high proportion of the residents had stained teeth, locally termed the "colorado brown stain". he took this information to greene vardiman black, a prominent american dentist of the time. after examining specimens of affected enamel, in 1916 black described the condition as "n endemic imperfection of the enamel of the teeth, heretofore unknown in the literature of dentistry." they made the interesting observation that although the mottled enamel was hypomineralized, and therefore should be more susceptible to decay, this was not the case. gradually, they became aware of existing and further reports of a similar condition worldwide. in 1931, 3 different groups of scientists around the world published their discoveries that this condition was caused by fluoride in drinking water during childhood. the condition then started to become termed "dental fluorosis". through epidemiological studies in the us, henry trendley dean helped to identify a causal link between high concentrations of fluoride in the drinking water and mottled enamel. he also produced a classification system for dental fluorosis that is still used in modern times, dean's index. as research continued, the protective effect of fluoride against dental decay was demonstrated.