A method of obtaining a preparation of biological origin for oral hygiene to prevent the onset of tooth decay, comprises steps of fermentation of bacteria in a culture medium, separation of the same and purification of the culture medium in which the bacteria have been cultivated, the step of fermentation of bacteria including a combined addition of starch and cellulose to the culture medium to the final concentration in the culture medium between 0.2 g/l and 2 g/l, and preferably of 0.5 g/l each.
