Which statement correctly describes the action of a fixed orthodontic appliance?

Which statement correctly describes the action of a fixed orthodontic appliance?

• A. Functional
• B. Intermittent
• C. Mechanical
• D. Passive

Answer: (C)

Fixed orthodontic appliances move teeth through mechanical forces transmitted from the archwire through brackets to each tooth. The brackets and wire form a rigid system that applies continuous, controlled pressure, guiding tooth movement as the wire tries to return to its preformed shape and as moments and torques are generated. This mechanical act is what drives tooth movement, via bone remodeling, rather than relying on muscle function or passive settling. Functional appliances work by altering muscle forces, while passive appliances don’t apply active forces, and intermittent action would only occur if forces weren’t maintained. So the action of a fixed appliance is mechanical.

Fixed orthodontic appliances move teeth through mechanical forces transmitted from the archwire through brackets to each tooth. The brackets and wire form a rigid system that applies continuous, controlled pressure, guiding tooth movement as the wire tries to return to its preformed shape and as moments and torques are generated. This mechanical act is what drives tooth movement, via bone remodeling, rather than relying on muscle function or passive settling. Functional appliances work by altering muscle forces, while passive appliances don’t apply active forces, and intermittent action would only occur if forces weren’t maintained. So the action of a fixed appliance is mechanical.