Effects of Positions and Magnitudes of Preactivation Bends on the Force Systems Generated by Orthodontic Stainless Steel T-Loop Springs

Abstract

Space closure of any kind in orthodontic treatment first needs a determination of the anchorage requirement. The clinician should control the force system accurately to achieve the differential space closure depending upon the diagnosis and treatment goals. Orthodontic T-loops have been used widely to close spaces. Several modifications have been made to achieve differential space closure. However, each modification has some clinical limitation and disadvantage. The purpose of this study is to look at the effects of preactivation bend position and magnitude on the force system and the possible implications in differential space closure. Five groups of orthodontic T-loops were studied. Each experimental group consisted of 20 T-loops and the positions or magnitudes of the preactivation bends were changed in each group. The forces and moments were measured, and the M/F ratios were computed. This study showed that the magnitude of the moment increased if (a) the preactivation position move closer to the bracket, or (b) the magnitude of preactivation is increased. There were extrusive forces acting on the side where the preactivation bends were closer to the bracket, or where the greater magnitude of preactivation existed.