Mechanical force generated by the activated orthodontic appliance is transmitted to and through tooth crown attachments, through the tooth as a whole, and into the periodontium by means of root- ligament-bone contact. The presence of such force, in addition to that of normal physiologic activity, deforms the supporting tissues and catalyzes their remodeling (initiated at the cellular level), in time allowing tooth-displacement beyond that permitted by simply by deformation of the periodontal ligament. The """"""""universal"""""""" orthodontic bracket, appropriately ligated, independent of clinical philosophy and technique, permits the delivery of force in all three planes of space. This force or force-system may be expressed in the form of six concentrated components (with respect to a local reference frame): three forces and three mechanical couples. Mechanical forces exist not individually, but in pairs;; two bodies, the""""""""deliverer"""""""" and the """"""""receiver,"""""""" are required to generate force. Within the pair, the two forces are identical in magnitude, direction, ( and also location if the forces arise from physical contact), but are of opposite sense. With application to orthodontic mechanics, the """"""""deliverer"""""""" is/are the activated element(s) of the appliance, and the """"""""receive"""""""" is the crown-attachment or bracket. With reference to the application at hand, the instrument(s) to be designed, in use will (each) substitute for the orthodontic bracket. To date the orthodontist has had access to only simple instrumentation, and has been able to measure only forces, e.g. developed longitudinally in an """"""""elastic,"""""""" or transmitted faciolingually or occlusogingivally by a deflected orthodontic wire. The instrument(s) envisioned are to be capable of quantifying components associated with the local reference- frame described. Such instrumentation potentially give the practitioner the capability to quantify more fully and, thereby, to better control the force-systems delivered by the appliance. In addition, clearly, the instrument(s) could be useful in clinical and on-the-bench (experimental) research.
