Fluoride is a naturally-occurring mineral that is added to tap water in many cities and is also present in many toothpastes, rinses, vitamins, and other products. Fluoride, in the right amounts, helps to strengthen teeth and reverse the early stages of cavities. The CDC has called the addition of fluoride to drinking water one of the ten greatest public health achievements of the 20th century. If ingested in excessive doses, fluoride can cause discoloration to teeth, and in extremely high doses can be harmful to health. However, a tiny smear of fluoride toothpaste (“pea-sized” in children over three, or the size of a grain of rice for younger toddlers and infants) is an extremely safe and effective way to fight the cavity process in children. Professional fluoride treatments in a dental office should also be administered twice a year for most children.