Hydroxyapatite refers to one of the prime components of and an important element of usual teeth and bone. It forms the matrix of teeth and mineral of the bone. It is the hydroxyapatite molecule that gives the teeth and bones their rigidity. These molecules can combine together to produce microscopic clumps.
About seventy percent of the bone comprises of the inorganic mineral hydroxyapatite that comprises calcium carbonate, calcium phosphate, calcium hydroxide, calcium fluoride, and citrate.