Torque Expression of Contemporary Self-ligating Bracket Systems
Abstract
Background: Self-ligating bracket systems in orthodontics have evolved over the years, but there is limited data regarding their ability to generate torque for efficient third-order tooth positioning.
Aim: To compare contemporary active self-ligating bracket systems against a passive self-ligating bracket system and a traditional twin bracket system in their ability to generate torque at different degrees and direction of wire rotation, in vitro.
Materials and Methods: Five bracket system groups of 0.022 inch slot size (twin bracket system Victory Series with elastic ligature [E-Vic]; passive self-ligating bracket system Damon Q [P-Dmn]; and active self-ligating bracket systems Speed [A-Spd], InOvation-R [A-Ovn] and Empower 2 Active[A-Emp]) were tested for torque expression utilizing a 0.019 x 0.025 inch stainless steel wire ligated into their slots. Single upper right central incisor brackets of each system were mounted using a specialized mounting jig, and a custom torque assembly fixed to an Instron materials testing machine was utilized to measure torque generated from -15 to +45 degrees of wire rotation. Ten clockwise and ten counterclockwise rotations were performed for each bracket system (n=20).
Results: Torque expression significantly varied between bracket systems with P-Dmn, E-Vic and A-Ovn generating the highest torque, and A-Spd and A-Emp the lowest, at most degrees of wire rotation. The direction of wire rotation had the largest effect on the A-Spd and A-Emp active bracket systems, whereby the counterclockwise rotation generated significantly more torque than the clockwise rotation tests.
Conclusions: All five bracket systems displayed different behaviors of torque expression when comparing degrees and direction of wire rotation. Understanding these differences in torque expression can help the clinician plan and provide treatment more efficiently.