Hydroxyapatite is a calcium-phosphate mineral complex that provides bone and teeth with their structural hardness and integrity. Medically, it has been used as an implant for bone and dental surgeries, in toothpaste, and as a supplement for dental health. Hydroxyapatite can be made synthetically from chemical salts, which may have some salt impurities and can have lower calcium levels, or it can be extracted from natural sources like fishbone, coral, bovine bone, eggshell, and seashells.^[3]

Hydroxyapatite is used in toothpaste to prevent caries and reduce dentin sensitivity.^[3] There’s not enough research to say how it measures up to fluoride.

As a dietary supplement, it has been used as a source of calcium to slow osteoporosis and for reducing osteoporosis-related pain. The forms found in dietary supplements include ossein-hydroxyapatite complex (OHC) and microcrystalline hydroxyapatite compound, both of which are sourced from powdered bone and contain bone proteins in addition to hydroxyapatite.^[1][4][5]

Hydroxyapatite has also been formulated as an injectable skin filler that is FDA-approved to cosmetically treat wrinkles and facial fat loss in people with human immunodeficiency virus (HIV).^[6]

No safety concerns have been reported for hydroxyapatite used in toothpaste.^[3] In supplements taken by mouth, ossein-hydroxyapatite has been used in studies for up to four years without safety issues, while microcrystalline hydroxyapatite has been used for up to one year.^[1][7] Common adverse effects are gastrointestinal (constipation, dyspepsia, abdominal pain, vomiting, etc) and seem to occur at a slightly lower rate than with calcium carbonate supplements.^[8][1] Since hydroxyapatite dietary supplements are typically from bovine sources, improper manufacturing processes might increase the risk of variant Creutzfeldt-Jakob disease(vCJD), also known as “human mad cow disease”.^[2][9][10]

Hydroxyapatite provides the hardness and support of bones and teeth in the body. Teeth are made of 70% to 80% large hydroxyapatite crystals, which are organized by matrix proteins such as amelogenins and enamelins, providing a framework for mineralization and demineralization of enamel. In the bone, nano-hydroxyapatite crystals in the shape of needles and plates are organized by a network of type-I collagen, resulting in the structural stability and hardness of bones.^[3] As a supplement, hydroxyapatite is a source of dietary calcium which reduces bone resorption, which is the body’s process of breaking down bones to ensure there is sufficient calcium in the blood. This contributes to increased bone mineral density and, theoretically, to stronger bones.^[2]