The invention relates to a helical ribbon mixing gear with a mixing vessel (1), the inside of which is axially symmetrical, and a motor-driven central agitator axis (2) with laterally extending agitator anus (30, 31, 32) to which at least one sloping helical ribbon (4) with a circular inclination in a direction of rotation (D) is attached, an outer edge of the helical ribbon (40) being positioned near to a mixing vessel wall (10), an outer tooth profile (50-52) being formed at the wall-sided edge of the helical ribbon (40), with a radial profile depth (T) which is smaller than a radially adjacent ribbon width (B), and with a circular tooth spacing (W) of one to ten times the profile depth (T).