Which type of tooth movement has the center of rotation coinciding with the center of resistance?

The type of tooth movement where the center of rotation coincides with the center of resistance is rotation produced by couple. In this type of movement, the forces are applied in such a way that they create a couple, which means there are two equal and opposite forces that produce rotation around the center of resistance. This allows the tooth to rotate more effectively in the desired direction without any translation or tipping.

Understanding that the center of resistance is essentially the point where a tooth resists movement helps clarify why this relationship is crucial for controlled rotation. When the center of rotation aligns with the center of resistance, it indicates that the tooth is undergoing a pure rotational movement about that central point, leading to accurate and predictable tooth movement.

In contrast, controlled or uncontrolled tipping involves movements where the center of rotation does not coincide with the center of resistance, which can result in undesired tooth displacement as well as rotation. Translation refers to a combination of movements that shift the tooth in a straight line, and the center of rotation does not remain fixed in relation to another resistance point, hence differing from rotation produced by a couple.