Orthodontic Force Systems Practice Test 2025 – The Comprehensive All-in-One Guide to Mastering Your Exam!

The center of resistance in a single-rooted healthy tooth is typically located about one-third to one-half down the root from the cemento-enamel junction (CEJ) to the apex. This positioning is significant because this area has adequate resistance to forces applied during orthodontic treatments.

When a force is applied to move the tooth, the center of resistance acts as a fulcrum that helps predict how the tooth will respond to those forces. Understanding the location of this center is crucial for effective and efficient tooth movement, especially in orthodontics, as it informs clinicians on how to apply forces properly to achieve desired movements without causing harm to the surrounding tissues.

The apex of the root is often not the location of the center of resistance since this would not provide the necessary mechanical advantage needed to move the crown of the tooth efficiently. The junction of the root and crown and the furcation area are also not the optimal locations, as they do not maximize the resistance and control necessary for precise tooth movement in orthodontic cases. Thus, the correct understanding of the center of resistance being around one-third to one-half down the root enhances the predictability and effectiveness of orthodontic treatments.