The effectiveness of differential moments in establishing and maintaining anchorage.

The purpose of the present study is to both clinically and cephalometrically investigate maximum and minimum anchorage control in four first premolar extraction cases, using the "differential moments (torque)" concept. Data were obtained from the pretreatment and posttreatment lateral cephalometric radiographs of 30 patients, 13 boys and 17 girls, who were treated exclusively with "differential torque" mechanics. Of the 30 patients selected, 18 were classified as having Angle Class I malocclusion (crowded and/or bimaxillary alveolar protrusion) and 12 as having Angle Class II, Division 1 malocclusion (crowded and/or severe overjet). The sample was divided into two groups, according to the severity of crowding. Subjects with 6.0 mm or more of crowding, in at least one quadrant per arch, were placed in the maximum anchorage group, suggesting the desirability of maintaining a relatively stable position of the anchor unit. Subjects with less than 6.0 mm of crowding per quadrant were categorized as moderate or minimum anchorage cases, indicating desirability of some intermediate degree of controlled movement of the anchor teeth. Comparison of the two groups in each malocclusion category revealed their comparability with respect to molar relationship and incisor overjet. The major finding of this study is the clinical effectiveness of differential moments as a means of controlling intraoral anchorage. It proves to be optimal and controllable for clinical purposes, regardless of the type of malocclusion or the severity of crowding.