What type of force generates a pure rotation around the center of resistance?

The type of force that generates a pure rotation around the center of resistance is a couple. A couple consists of two equal and opposite forces whose lines of action do not coincide. This arrangement results in a torque that causes rotational movement around a specified axis or point, such as the center of resistance in orthodontic terms.

When a couple is applied, it creates an equal and opposite moment about the center of resistance, allowing for dental movement that emphasizes rotation without translational force components. This is particularly useful in orthodontic treatment where controlled rotational movements of teeth are necessary to achieve optimal positioning and alignment.

In contrast, a moment force, while it can produce rotational effects, is typically associated with a fulcrum and may involve translation depending on how it is applied. A single force typically generates displacement but does not inherently produce rotation unless combined with another force. Net force is a vector sum of all forces acting on an object, and while it can involve rotational effects, it does not specifically indicate a pure rotational movement like a couple does.