1. The use of cationic surfactant obtained by condensation of fatty acids and esterified dibasic amino acids, having the formula (1):! ! where! X- is a counterion derived from an inorganic or organic acid, preferably Br-, Cl- or HSO4 -, or an anion based on a phenolic compound； ! R1 represents a straight alkyl chain of an unsaturated fatty acid or hydroxy acid containing from 8 to 14 atoms, linked to the α-amino acid group by an amide bond； ! R2 is a straight or branched alkyl chain containing from 1 to 18 carbon atoms, or an aromatic group； ! R3 represents! ! !or ! ! where n lies in the range from 0 to 4,! as protective agents for protecting teeth from pathological erosion. ! 2. The use according to claim 1, characterized in that the cationic surfactant is used in the form of compositions for oral use, such as sweets, confectionery, tablets, lozenges, candies, chewing gums, jams, jellies, dragees or dry powder mixtures intended for dissolving to produce drinks. ! 3. The use according to claim 1 or 2, characterized in that the composition for oral administration is a chewing gum or lozenge. ! 4. The use according to claim 3, characterized in that the compound of formula (1) is contained in the composition in a concentration of from 0.001 to 5 wt.%, Preferably from 0.001 to 2 wt.%. !5. The use according to claim 1 or 2 by eating, chewing or sucking the composition. ! 6. The use according to claim 3, characterized in that the compound is an ethyl ester of lauroylarginine hydrochloride. ! 7. Composition for oral administration, such as weak1. Применение катионного сурфактанта, полученного конденсацией жирных кислот и этерифицированных двухосновных аминокислот, имеющего формулу (1): ! ! где ! X- представляет собой противоион, производный неорганической или органической кислоты, предпочтительно, Вr-, Сl- или HSO4 -, или анион на основе фенольного соединения； ! R1 представляет собой прямую алкильную цепь ненасыщенной жирной кислоты или гидроксикислоты, содержащую о
