Fluoride is the best preventative dentistry available. The reason it gets a bad rap is because it can be dangerous if you ingest it in large quantities. The fluoride the dentist applies is not systemic (where you swallow it), it is applied topically and quickly hardens. It adheres to your tooth where the fluoride strengthens the tooth enamel and prevents small cavities from getting worse. The fluoride is brushed off after 4-6 hours of it being absorbed into the enamel of the tooth. The ADA and the major health organizations in the world today still say it’s one of the top ways to prevent tooth decay.