FIELD : medicine.SUBSTANCE : invention refers to medicine, namely to dentistry, and can be used for remineralisation of hard dental tissues in order to prevent and treat caries in the stain stage, hyperesthesia of hard dental tissues. Disclosed hydrogel contains, wt % : hydroxyapatite 10.0–15.0; xylitol 10.0–15.0; papain 3.0–5.0; potassium nitrate 3.0–5.0; carbopol 0.5–1.0; sodium hydroxide 10 % solution 2.0–3.0; sorbic acid 0.2–0.5; fragrance 0.3–0.5; highly pure water – balance.EFFECT : use of the agent provides higher acid resistance of the enamel, eliminates and prevents the progressing of the dental tissue demineralisation processes, reduced sensitivity, prolonged remineralisation effect due to prolonged contact of the remineralising gel with the surface of dental hard tissues, increased efficiency of therapeutic and preventive measures and reduced length of their carrying out.1 cl, 4 tbl, 4 ex, 2 dwg