Abstract: A process for the preparation of a hydroxyapatite, which is suitable as a tooth-cleaning substance, by precipitation from aqueous phosphoric acid and calcium hydroxide solution, in which a calcium-doped phosphoric acid solution is fed to an intensive mixer with a suspension of calcium hydroxide/oxide in a molar ratio of Ca:P=1.667 corresponding to the hydroxyapatite of and reacted there at precipitation temperatures of 60.degree.-100.degree. C., preferably 80.degree.-90.degree. C. and a pH of 4-8, preferably of 6.5-7.5. Also disclosed in a tooth-cleaning substance containing the hydroxyapatite.