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Torque

Torque

Torque is an important quantity for describing the dynamics of a rotating rigid body. We see the application of torque in many ways in the world, such as when pressing the accelerator in a car, which causes the engine to apply additional torque on the drivetrain. Here, we define torque and provide a framework to create an equation to calculate torque for a rigid body with fixed-axis rotation.
Torque can be considered as the rotational counterpart to force. Since forces change the translational...

Net Torque Calculations

Net Torque Calculations

When a mechanic tries to remove a hex nut with a wrench, it is easier if the force is applied at the farthest end of the wrench handle. The lever arm is the distance from the pivot point (the hex nut in this case) to the person’s hand. If this distance is large, the torque is higher. Only the component of the force perpendicular to the lever arm contributes to the torque. Therefore, pushing the wrench perpendicular to the lever arm is more advantageous. If multiple people apply force to rotate...

Self-Locking Screw

Self-Locking Screw

A square-threaded screw jack is a mechanical device widely used for lifting heavy loads or applying considerable force. One of the key features that can make a screw jack more effective and reliable is its self-locking capability.
A square-threaded screw jack carrying a load is considered self-locking if the screw retains its position even after the moment applied to it is removed.

Frictional Forces on Screws

Frictional Forces on Screws

Screws are characterized by a helical ridge known as a thread wrapped around a cylindrical shaft. They are commonly used as fasteners to hold objects together or to transmit power and motion in machines. One type of screw that is particularly useful for transmitting power is the square-threaded screw.
A jack with a square-threaded screw is a mechanical device used to lift heavy loads by applying a force at its handle. When the force is applied, the screw turns, raising the load. The screw can...

Machines: Problem Solving I

Machines: Problem Solving I

A toggle clamp is a mechanical device commonly used for holding and clamping objects in various applications, such as woodworking, metalworking, and assembly operations. Consider a toggle clamp subjected to a force of 200 N at the handle. The vertical clamping force can be calculated, provided the dimensions of the toggle clamp are known.
The toggle clamp system is a machine structure consisting of movable, pin-connected multi-force members that form a stabilized system to transmit forces. The...

Screw: Problem Solving

Screw: Problem Solving

In mechanical engineering, the interaction between a threaded screw shaft and a plate gear involves analyzing the resisting torque on the plate gear that can be overpowered when a specific torsional moment is applied to the shaft. To better comprehend this concept, consider a generic situation with a threaded screw shaft with a given mean radius and lead and a plate gear with a specified mean radius. The coefficient of static friction between the screw and gear is also provided.
To evaluate the...

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Related Experiment Video

Updated: Jul 5, 2026

Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires

Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires

Published on: July 24, 2018

Torque expression of self-ligating brackets.

Hisham M Badawi¹, Roger W Toogood, Jason P R Carey

¹Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.

American Journal of Orthodontics and Dentofacial Orthopedics : Official Publication of the American Association of Orthodontists, Its Constituent Societies, and the American Board of Orthodontics

|May 6, 2008

Summary

Active self-ligating brackets provide superior torque expression compared to passive self-ligating brackets. This difference is crucial for achieving ideal incisor inclination and stable occlusion in orthodontic treatments.

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Area of Science:

Orthodontics
Biomaterials Science
Dental Mechanics

Background:

Labiolingual inclination of incisors is key for dental esthetics and occlusion.
Rectangular archwires in rectangular bracket slots enable third-order control.
Self-ligating brackets offer potential advantages in orthodontic mechanics.

Purpose of the Study:

To compare the third-order moment delivery of active versus passive self-ligating brackets.
To quantify torque expression differences between bracket types using specific archwires.
To evaluate the influence of bracket design on orthodontic torque control.

Main Methods:

Development of a novel bracket/wire assembly torsion device.
Measurement of torque and torsion angle using a multi-axis force/torque transducer and digital inclinometer.
Testing of 50 maxillary right central incisor brackets from four manufacturers (two active, two passive).

Main Results:

Active self-ligating brackets initiated torque expression at a lower angle (7.5°) than passive brackets (15°).
Higher torque expression was observed with active brackets up to 35° of torsion.
Torque increased linearly with further torsion for Damon2, Smart Clip, and In-Ovation brackets, while Speed bracket torque plateaued.

Conclusions:

Active self-ligating brackets demonstrate greater effectiveness in torque expression than passive self-ligating brackets.
The findings suggest active brackets may offer more precise control over incisor inclination.
Understanding bracket mechanics is essential for optimizing orthodontic treatment outcomes.