The movement of a tooth under the influence of an orthodontic appliance is dependent upon the acting force and the resulting moment. This moment can be computed by adding the inherent moment of the force and the therapeutic moment of the appliance. The article points out the differences between these two kinds of moments. Moreover, it describes, that the resulting moment is the base for another kind of moment-to-force-ratio, Mi/F', which is the only parameter to predict the direction of orthodontic tooth movement.
Biomechanical Phenomena Dental Stress Analysis