The main elements of tooth enamel are calcium and phosphate ions. The crystalline hydroxyapatite that makes up 96% of tooth enamel and the calcium and phosphate ions in saliva are in a stable balance under normal circumstances. Demineralization, a process that results in the disintegration of tooth mineral (hydroxyapatite), occurs when the pH falls below a certain level (about 5.5 for enamel and 6.2 for dentin). Remineralization is the process by which minerals are reincorporated into the tooth when the pH is raised by the natural buffering ability of saliva.

Fluorapatite, rather than hydroxyapatite, occurs during the remineralization process when fluoride is present in oral fluids (i.e., saliva). When the apatite crystal lattice is formed, fluoride ions take the place of hydroxyl groups. The rate of remineralization is accelerated by fluoride. Even in acidic environments, fluorapatite has a lower intrinsic solubility than hydroxyapatite. Fluorapatite will develop when hydroxyapatite dissolves in an acidic environment if fluoride is present. Your enamel becomes thicker and more resistant to deterioration as a result of fluoride in toothpaste.