The force requirements for tooth movement, Part I: Tipping and bodily movement.

Specific data on the relation between force and tooth movement is essential not only to facilitate non-traumatic orthodontic treatment but also to establish a sound basis for appliance design. Whilst the broad approaches to orthodontic tooth movement appear to be the application of tipping and/or bodily movement, no scientific comparison between these two types of movement has yet been made. This article describes experiments which repeat investigations of Storey and Smith into the relation between the force applied and the rate of tipping movement and their extension to include bodily movement. Twenty adolescent male patients requiring distal movement of upper cuspid teeth as a part of orthodontic treatment were each fitted with calibrated cuspid retraction springs. The appliances were designed to induce bodily movement on one side of the mouth concurrently with tipping movement on the other. Initial force applications were identical, and the experiments lasted for up to eleven weeks following one activation of the retraction springs. The results of these experiments were compared with those of other workers, and an explanation of the causes of the past controversy regarding various theories of tooth movement is offered.