Mechanical Analysis of the Begg Torquing Auxiliary

An experimental program was undertaken to evaluate the four-spur torquing auxiliaries used in the Begg technique of orthodontic treatment. A laboratory testing apparatus was specifically designed for torque research; it enables separation of the torque from other incisor force system components. Three wire sizes and two spur angles were studied; lingual root torque and vertical displacements and forces associated with wire/bracket engagement and deactivation of the torquing auxiliary were measured for various angular. positions of the incisors. Twelve specimens for each of six subsamples were prepared and tested; the data were statistically analyzed.

Five of six of the auxiliaries tested were capable of sufficient torque to place the incisors at the desired finished angulation. Torsional stiffness of the auxiliary increased with increased wire size, but deactivation rate appears to be independent of spur angle. No auxiliary generated sufficient torque to exceed an average value in an optimum torque range, the value derived systematically and judged to be physiologically acceptable. Lingually-directed holding forces against the incisors were quantified and Class II elastics sizes suggested in relation to torque magnitudes to place incisor centers of rotation at bracket level or slightly occlusal thereto.

Activation of lingual root torque with the auxiliary produces a vertical displacement potential in the incisor area; extrusive forces generated without allowance for this phenomenon were found to be of substantial magnitude. Suggestions toward nullifying this undesirable side effect, which is generally magnified by the presence of Class II mechanics, concluded this project.