The basis of orthodontic therapy is the ability to control the force system applied to the teeth. Yet, the relationship between the point at which a given force is exerted on a tooth and the center of rotation (CRot) for the movement that such force produces is not completely understood. [1] Orthodontic forces can be treated mathematically as vectors. When more than one force is applied to a tooth, the forces can be combined to determine a single overall resultant. Forces can also be divided into components in order to determine effects parallel and perpendicular to the occlusal plane, Frankfort horizontal, or the long axis of the tooth.Forces produce translation (bodily movement), rotation, or a combination of translation and rotation, depending on the relationship of the line of action of the force to the center of resistance of the tooth. The ratio between the net moment and net force on a tooth moment to force ratio (male/female ratio) with reference to the center of resistance determines the CRot. Since most forces are applied at the bracket, it is necessary to compute equivalent force systems at the center of resistance in order to predict tooth movement. [2] The study of teeth displacement following the application of orthodontic loading regimes is not trivial as it depends on several and complex parameters such as material properties of periodontal tissues, shape and length of tooth, width of

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