In laboratory research there were studied different combinations of remineralizing agents allowing production of substances close by chemical composition to hydroxyapatite of hard dental tissues. The most acceptable for practical use in case of demineralizing foci of hard dental tissues treatment can be only 2 calcium orthophosphates that may be synthesized under physiological conditions from solutions of calcium nitrate and twice-substituted ammonium phosphate, in particular, dicalcium phosphate dihydrate (structure of brushite, CaHP0(4) x 2H(2)O) and the so called precipitated hydroxyapatite (Ca(10-x) (HPO(4))(x)(PO(4))(6-x)(OH)(2-x)). The data are the bases for development of remineralizing agents and their further experimental and clinical studies.