Impact of passive self-ligation and conventional elastic ligation on orthodontic force in the simulation of a mandibular lateral incisor linguoversion

Abstract

This study compared three-dimensional forces delivered to the displaced tooth and its adjacent teeth between passive self-ligation (PSL) and conventional elastic ligation (CL) in simulation of mandibular lateral incisor linguoversions. A multisensor system was used to measure three-dimensional forces delivered to brackets attached to the mandibular left central incisor, lateral incisor, and canine (FDI tooth numbers 31, 32, and 33, respectively). Two ligation methods (PSL and CL), 3 nickel-titanium (0.014-inch) archwires similar to the arch form of normal occlusion, and 2 displacements (1 and 4mm) were tested. In 1-mm displacement, forces were significantly smaller in CL than in PSL at 32 in the labial direction and larger at 31 in the mesial direction for all 3 types of archwires (P<0.01 for both). For 2 of 3 archwires, forces were larger in CL than in PSL at 33 in the lingual direction (P<0.01). In 4-mm displacement, forces were significantly larger in CL than in PSL at 31 in the mesial direction and significantly smaller in CL than in PSL at 33 in the distal direction for all 3 archwires (P<0.05 and P<0.01, respectively). Mean forces in the vertical direction were small, ranging from -0.05 to 0.05N. Under a small amount of displacement, force magnitude in PSL was smaller than that in CL at the displaced tooth in labial-lingual directions. Under a large amount of displacement, a more "open coil spring effect" was significantly obtained in CL than PSL at both adjacent teeth of the displaced tooth.