It is likely thatthe sites of S. mutans in the ecosystem are occupied by other bacterial species, so that the return of S. mutans is impaired.The composition according to the invention contains preferably a fluoride such as sodium fluoride, other fluorides than sodium fluoride are eligible too: e.g. stannous fluoride, aminfluoride and sodiummonofluorophosphate, because by usingfluoride compounds t