Apatite and hydroxyapatite are both minerals and belong to the calcium phosphate family. There are a number of different calcium phosphates. Hydroxyapatite is the most stable and the most important calcium phosphate for humans, as it forms the mineral phase of bones and teeth. The chemical formula of hydroxyapatite is: Ca5(PO4)3(OH).
Hydroxyapatite plays an essential role in the human body. It forms the basis for teeth and bones. In both cases, hydroxyapatite is responsible for their hardness. Unlike many other active ingredients used in dental care, hydroxyapatite occurs naturally in the human body.