Torque Expression of Active and Passive Self-Ligating Orthodontic Brackets with Different Stainless Steel Wire Sizes
Abstract
This investigation aimed to compare engagement angles and torquing moments generated by stainless steel (SS) wires in three active self-ligating (ASL), one passive self-ligating (PSL), and a conventional twin orthodontic bracket system control. Brackets were tested in simulations of buccal and palatal root torque using four sizes of SS wires (16x22, 17x25, 19x25, 20x20 mil). A custom 3D printed testing apparatus was developed to measure torque. After initial engagement within bracket slots, torquing moments increased with progressive rotation of brackets around wires. In general, the PSL and conventionally ligated systems generated significantly larger torquing moments than ASL systems, especially with larger wires and greater degrees of twist. Torquing direction only influenced torque expression with ASL systems. The PSL system demonstrated significantly smaller engagement angles than the ASL or twin bracket systems, especially with larger wires. In addition to ligation modality, other aspects of bracket design likely contribute to these findings.