Fluoride is a natural element that can be found in many places, like the water we drink and the food we eat. Decades ago, scientists began to notice that children who lived in places where fluoride occurred naturally in the water had fewer dental cavities. As teeth are developing, fluoride safely strengthens the enamel - the hard outer 'shell' of the tooth, and helps to prevent the development and spread of cavities. Use of a fluoride toothpaste or rinse can help to prevent decay. Fluoride can be found in a number of over-the-counter options:
Best over-the-counter fluoride sources:Anti-cavity fluoride rinse, e.g. ACT anti-cavity fluoride rinse or Listerine with fluoride. Also, any fluoride toothpaste with an ADA endorsement, e.g. Crest, or Colgate.
Common food/drinks that contain fluoride: GreenTea, Grape juice, Fish, and Chicken.
Read more from the American Dental Association Here