Fluorosis due to excessive fluoride intake - almost one in four children is affected. Fluorosis is a chalky-white enamel stain on the permanent incisors. They are caused by a disruption of mineralisation during tooth maturation. The cause is excessive fluoride intake during the tooth maturation phase. The phase around the second and third up to the fifth year of life is considered to be particularly sensitive. The risk is particularly high in children because their low body weight makes them susceptible to overdosing and they often swallow toothpaste when brushing.