Electronic Thesis and Dissertation Repository

Thesis Format



Master of Clinical Dentistry




Tassi, Ali

2nd Supervisor

Burkhart, Timothy



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.

Summary for Lay Audience

For many reasons, it is important to properly position teeth within the mouth. Many different bracket systems are commonly used in orthodontics to move the front teeth as desired. These different systems often have varying ways to secure the archwire to the bracket, resulting in different forces generated. This study was designed to test the ability of five different contemporary orthodontic bracket systems to produce torque. A custom set-up was made to twist a commonly used archwire inside of an orthodontic bracket. This was done from -15 to +45 degrees for each of the five bracket systems, in both the clockwise and counterclockwise directions. Results were compared to one another and other studies to evaluate how efficient each group was at producing torque in both directions.