Two-vector mechanics.

The conventional orthodontic appliance is not without its limitations for certain types of tooth movements; in particular, if the appliance cannot access the area to elicit the type of force vector for a particular displacement. Examples of such movements are: space closure by translation, uprighting and intrusion of posterior teeth, intrusion with retraction and lingual root torque of anterior teeth. In this paper we describe a mathematical method to design an appliance system that overcomes these difficulties. This system includes two statically determined elements and allows for highly controlled force vector application point and direction. A clinical case of midline discrepancy is shown to demonstrate the clinical use and utility of this method.