Fluoride

People often ask how fluoride works to prevent root decay and decrease sensitivity of teeth. Well first, the hardness of teeth comes from a form of calcium called hydroxyapatite. This is the same substance that makes bone hard. Bone however has a blood supply throughout your life which helps bone to repair while enamel does not. That leaves the teeth susceptible to attack especially by acids formed by the bacteria in plaque. The acid breaks down the hydroxyapatite and the soft part of the tooth begins to decay or get hypersensitive.

Fluoride ions attack the hydroxyapatite as well. Instead of causing destruction of this substance, it causes their transformation into fluoroapatite. The fluoride ion essentially substitutes itself for the hydroxyl groups in the hydroxyapatite. This new formation is more resistant to acids and the breakdown process. Thus, rinsing and brushing your teeth with fluoride products coats the outside of the teeth with a layer of acid resistant fluoroapatite. Also, fluoride has been shown to penetrate leaky fillings to partially remineralize some decay beneath them or very small cavities between teeth.