Dental fluorosis is a condition caused by a child receiving too much fluoride during tooth formation (i.e. up to the age of six). Mild fluorosis can lead to fine, white streaks on the permanent teeth. With moderate fluorosis, visible changes of a cosmetic concern on the surface of teeth may be noticeable. In severe fluorosis, teeth may appear stained and pitted. In Canada, moderate or severe fluorosis is extremely rare. Scientific studies have not found a credible link between fluoride at the levels typically found in drinking water and any other negative health effects.