Dentist put a coating of fluoride on my teeth. what is this for?

Topical Fluoride: It strengthens the surface of the enamel making it harder and more resistant to tooth decay. However, you still need to watch your diet (avoid sticky starchy foods high in unrefined sugar) and exercise proper oral hygiene with both tooth brushing and flossing after meals.

Decrease decay: Fluoride will strengthen your teeth and help to prevent decay. Remember you still need good brushing, flossing and a healthy diet.

4 mechanisms: 1) when Fluoride is incorporated into the tooth's enamel it makes it harder for the enamel to lose minerals when exposed to an acid challenge. 2) when Fluoride is in the saliva it makes it easier for the enamel to pick back up minerals that it has lost. 3) Fluoride inhibits the oral bacteria's ability to produce acid. 4) Fluoride inhibits the oral bacteria ability to stick to the teeth.