Orthodontic headgear is an external appliance used with traditional braces to address complex jaw alignment and bite issues that internal dental forces alone cannot correct. Braces primarily align individual teeth within the arch but are limited in applying the large, sustained forces required to influence the position of the entire jaw or significantly move large teeth like molars. For certain skeletal or dental discrepancies, the orthodontist must use a device that transfers force from outside the mouth to guide growth and reposition teeth effectively. This external support achieves a stable and functional bite correction, especially in growing patients.
What Orthodontic Headgear Is
Headgear is an extra-oral device, worn partially outside the mouth, that applies controlled pressure to the jaw and teeth. It consists of three primary components that deliver this force. The first is the facebow, a U-shaped metal wire with an inner bow that connects to bands fixed on the back molars.
The outer bow of the facebow extends outside the mouth, attaching to the second component: the headcap or neck strap. This strap, typically made of fabric or plastic, fits around the back of the head or neck, serving as the stable anchor point. The third component involves the molar bands, small metal rings cemented onto the back teeth that contain tubes to receive the inner bow.
Elastic bands or springs connect the outer facebow to the headcap or neck strap, generating the precise, continuous force needed for movement. This design allows the force to be applied directly to the molars or the entire upper jaw structure. The apparatus is removable, allowing the patient to take it off for eating, brushing, and certain activities.
The Necessity of External Anchorage
The need for headgear stems from a fundamental law of physics: for every action, there is an equal and opposite reaction. In orthodontics, attempting to move a tooth generates a reactive force on the anchor teeth holding the archwire, risking unwanted movement. This concept, known as reciprocal force, limits what internal appliances can achieve.
If an orthodontist wants to move the front teeth backward to correct a large overjet, they must use the back molars as an anchor point. The force used to pull the front teeth back simultaneously pushes the anchor molars forward, leading to a loss of space. This unintended forward shift of the molars is called anchorage loss.
Headgear solves this problem by providing external anchorage, using the robust structure of the head or neck to dissipate the reactive force. Transferring the opposing force to a stable, non-dental structure allows the molars to be held firmly in place or moved backward without causing the anchor teeth to shift. This external resistance allows for significant movement of the target teeth while maintaining the position of the rest of the dental arch.
Directing Force and Specific Movement
Headgear applies directional forces that are either impossible or inefficient to achieve using only fixed braces. One primary application is molar distalization, the process of pushing the upper molars backward to create space for crowded front teeth. A light, stable force, often between 3 to 9 Newtons, is applied to achieve a measured movement rate of approximately 1 millimeter per month.
The appliance is also effective in growth modification, guiding the development of jaw bones in growing adolescents. By applying specific forces to the upper jaw (maxilla), headgear can restrict its forward growth, allowing the lower jaw (mandible) to catch up. This approach is common for correcting an excessive overjet, where the upper front teeth protrude significantly.
The type of headgear used depends entirely on the desired angle of force, which determines the movement achieved. Cervical-pull headgear, featuring a neck strap, applies a low, backward, and slightly downward force, often used to move molars backward. Conversely, high-pull headgear uses a strap over the back of the head, applying a high, backward, and slightly upward force to control vertical growth or intrude the molars.
A third type, the reverse-pull headgear (or face mask), corrects underbites by applying a forward force to the upper jaw. This external traction encourages the maxilla to grow forward, establishing a proper relationship with the lower jaw. For these movements to succeed, the appliance must be worn consistently, requiring a minimum of 12 to 16 hours per day for effective skeletal and dental change.