Controlling the magnitude, direction, and duration of extraoral force.

T he purpose of this article is twofold: First, it will demonstrate the clinical application of precise control of t,he magnitude, direction, and duration of extraoral force and, second, cases will be presented to demonstrate how control of these three mechanical variables dramatically increases the efficiency and effectiveness of extraoral force in the treatment of malocclusion. The subject will be introduced by showing a case (Case 1) in which 44 ounces of bilateral extraoral force was applied in a precise and predictable direction 24 hours per day for 97 days (Fig. 1). The patient was 11 years 5 months of age at the beginning of treatment; dentally, she was in the late mixed-dentition stage. She had an ANB angle of 6 degrees, a Frankfort-mandibular plane angle of 32 degrees, an end-to-end molar relationship, 11 mm. of overjet, and a slight open-bite. There was adequate space in the lower arch. The appliance consisted of edgewise bands on the upper and lower incisors and first molars, The objective in the lower arch was to round out the flattened arch form, to move the incisors slightly labially, and to maintain arch length (Fig. 1, P). The objective in the upper arch was to simultaneously move the upper first molars and four incisors distally and bodily, as a unit, by applying '(heavy " continuous, directional, extraoral force. A 0.021 by 0.025 inch edgewise wire was used to control the incisors. Eleven days after banding, the extraoral force was applied. Fig. 1, A through H, demonstrates the predictable change. The original models were taken 355 months before treatment began. Except for normal tooth eruption, the malocclusion remained essentially the same. Progress records taken after 97 days of controlled extraoral force show a normal molar relation and elimination of the 11 mm. of overjet.