Using Fluoride to Protect Your Teeth
Fluoride is effective in preventing cavities and tooth decay by coating your teeth and preventing plaque from building up and hardening on the tooth's surface.  Fluoride comes in two varieties, topical and systemic:
Topical fluoride is applied directly to the tooth and includes toothpastes and mouth rinses.
Systemic fluorides are generally only used by your dentist and are not often available for at-home use.  Systemic fluoride treatments are generally designed to help protect the oral health of children undergoing dental procedures.  Fluoride used in the dentist/orthodontists office is often a much stronger concentration than in toothpaste or mouthwash, but is available at some drug stores or pharmacy (ask your dentist before purchasing professional strength fluoride).