Fluoride is probably the most effective treatment available for preventing and limiting the spread of tooth decay. It is a naturally occurring mineral found in foods and drinks, such as fish and tea, but it can also be synthesized (manufactured). Synthetic fluoride is used in toothpaste, from which most people get their fluoride.
Fluoride protects teeth by strengthening the enamel, making teeth more resistant to acid attacks that can cause tooth decay. It reduces the ability of plaque bacteria to produce acid, and enhances the repair (remineralisation) of enamel.
If your cavity is in its early stages, your dentist may be able to repair the decay by using a concentrated fluoride gel, varnish or paste.