During which movement is the center of rotation located at infinity?

The center of rotation being located at infinity corresponds to a translational movement of the teeth. In orthodontics, translation refers to the movement where a tooth moves in a straight line, maintaining its position relative to the bone without any rotation. This type of movement effectively shifts the entire tooth in a linear fashion.

When the center of rotation is at infinity, it implies that the tooth is moving as if it's a rigid body, which results in a parallel shift without altering its axial inclination. Therefore, the tooth maintains its original orientation throughout the movement, making it a key characteristic of translation.

The reason other movements do not have the center of rotation at infinity is that they involve some degree of rotation or tipping around a center of rotation that is typically located within or near the tooth's root. For example, controlled tipping and uncontrolled tipping involve varying degrees of rotational movement, and reverse tipping specifically entails tilting back the incisal edge of a tooth. These movements all have defined centers of rotation located within the dental structure, rather than at an infinite distance.