Fluoride Protect Your Child’s Teeth Against Cavities Why is fluoride needed? Teeth are covered with a sticky film of germs, called plaque. Plaque uses the food we eat to make acids that cause cavities. Fluoride fights the acids that cause cavities by making teeth stronger. Even before teeth come in, fluoridated water can make teeth stronger. After teeth come in, fluoride treatments, fluoridated water, and fluoride toothpaste protect against cavities. How can my child get fluoride? Drink fluoridated water. Brush teeth with fluoride toothpaste. (A pea-sized amount is all that is needed) Use a fluoride mouth rinse after age 6. See a dentist for regular fluoride treatments.