bag the control unit will first read out the filling level stored there but this level is then reduced each time the toothbrush is operated decreasing it by an amount that depends on consumption the prevailing filling level or the amount of application substance consumed is transmitted to the data carrier 13 of the toothbrush bag 9 when operation of the toothbrush stops so that when operation of the toothbrush is resumed again or after changing and replacing the toothbrush bag 9 the prevailing filling level is stored there and thus the filling level display is displayed correctly even when the application substance reservoir inserted into the toothbrush is not completely full user specific data may advantageously also be stored in the data carrier 13 to control the operation of the toothbrush in a user specific manner as a function of the stored data this is appropriate for example when the hand part 2 is used by multiple users who use different application substances however even when the same toothbrush bag is being used user specific data may still be stored in the data carrier 13 for example different toothpaste dispensing quantities may be defined for different users so that each user receives the amount of toothpaste he she desires even if only one user is defined different dispensing amounts.