What movement occurs when Mf is less than Mc?

When the magnitude of the force acting on a tooth (Mf) is less than the moment created by the center of resistance (Mc), the primary effect that takes place is root movement. This situation indicates that the force is not strong enough to create a significant tipping or rotational effect around the center of resistance. Instead, the tooth moves in a way that emphasizes the displacement of the root more than the crown, which results in a more linear movement of the entire tooth.

In orthodontics, this type of movement is essential for aligning the roots of teeth within the alveolar bone, as it allows for a more controlled and stable repositioning of the tooth in three-dimensional space. Understanding this concept is critical for achieving desired tooth positions and maintaining optimal periodontal health.