PRE-HEALTH_Moment Arm of a Tooth
Instructions
This simulation shows how the moment arm can be manipulated to change the torque.
Use points A and B to move the tooth around. A will translate the tooth and B will rotate the tooth about point A. The CoRES (center of resistance) of the tooth is shown with a green dot in the root of the tooth.
The labeled bracket point represents where the force is being applied. It can be moved to any part of the exposed tooth. The vector displacement from the CoRES to the bracket is represented by . To change the force applied to the bracket, move the green dot at the end of the purple force vector . The green angle θ is between the COR, the bracket, and the direction of the force’s application. As the bracket and force are moved will change leading to changes in the torque.
In orthodontics, forces are represented in grams, lengths in millimeters, and torques in gram millimeters. By checking and unchecking the “change units” button the force, lengths, and torque will change from those used in orthodontics to SI units students may be more familiar with.
For more clarity on the geometry of the force/lengths, the tooth can be hidden by unchecking the "show graphics" box.
Created by Lewis Hicks, Priya Jamkhedkar, and Annelise Cummings for the Portland State University Physics Department, 2025.