Treatment tools for the mechanical treatment of high-consistency fibrous material, and preferably for dispersing waste paper. The treatment tools are provided with teeth and are moved past one another with tight spacing so that the fibrous material disposed between treatment tool may be subjected to high shearing forces. Because of the intense loading of the teeth, the teeth may be arranged together in groups. The groups established according to at least two different, predetermined axial length gaps between each of the teeth of the treatment tools. As a result, a higher mechanical strength of the teeth is achieved and a large through flow area is offered for the material to be treated.