Torque Expression of Active and Passive Self-Ligating Orthodontic Brackets with Different Archwire Materials
Abstract
This study aimed to compare torquing moments, engagement angles, and torsional stiffness generated by stainless steel (SS), titanium molybdenum alloy (TMA) and nickel titanium (NiTi) 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. A custom 3D printed testing apparatus was developed to measure torque. In general, the PSL and conventionally ligated systems generated significantly larger torquing moments than ASL systems, especially with stiffer 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 stiffer wires. Torsional stiffness values aligned with the expected modulus of elasticity of the given wire material. In addition to ligation modality, other aspects of bracket design likely contribute to these findings.