Functional Appliances for Adolescents

Functional appliances are orthodontic devices that work by harnessing the natural growth of the adolescent jaw to guide its development in a more favourable direction. Rather than simply moving teeth, they influence the position, relationship, and development of the jaws themselves — making them a uniquely powerful tool during the growth years.

They are most effective during the adolescent growth spurt, when the jaws are actively developing and the body is most responsive to the forces that functional appliances deliver. Outside of this window, the same corrections often cannot be achieved non-surgically.

At Lusk Orthodontics, functional appliances are used as a carefully timed component of treatment for adolescents whose jaw relationship would benefit from growth guidance, and are available in both removable and fixed forms depending on the needs of the individual patient.

How Functional Appliances Work

The jaws do not grow in isolation — their development is influenced by the forces placed upon them. Functional appliances work by repositioning the lower jaw and altering the muscular forces acting on the dental arches, which in turn stimulates a change in the direction and amount of jaw growth. Over time, this can produce a meaningful correction in the relationship between the upper and lower jaws — improving the bite, the facial profile, and the skeletal foundation on which subsequent orthodontic treatment can build.

The timing of functional appliance therapy is critical. Treatment is most effective when initiated at or just before the peak of the adolescent growth spurt — typically between the ages of 11 and 14, though this varies between individuals. A specialist assessment, including the review of a hand-wrist X-ray or cervical vertebral maturation stage, can help determine where a patient is in their growth cycle, allowing treatment to be timed for maximum effect.

Removable Functional Appliances

Removable functional appliances are worn by the patient and can be taken out for eating, cleaning, and sports. They must be worn consistently — typically 16 to 20 hours per day — to achieve the planned jaw correction.

Common removable functional appliances include the Twin Block, the Bionator, and the activator-type appliances, each of which works by holding the lower jaw in a forward position, stimulating the condylar growth and remodelling needed to correct a recessed lower jaw and prominent overbite.

Advantages: Less discomfort during the initial adjustment period; can be removed for contact sports; easier to maintain oral hygiene.

Requirement: Compliance is essential. The effectiveness of removable appliances is directly related to how consistently they are worn. For motivated adolescent patients who will commit to wearing the appliance as directed, removable functional appliances can produce excellent results.

Fixed Functional Appliances

Fixed functional appliances are bonded or attached to the teeth and cannot be removed by the patient. They deliver the corrective forces continuously — 24 hours a day — without relying on the patient’s compliance.

Examples include the Herbst appliance, the Forsus springs, and the Carriere Motion Appliance, all of which work by holding the lower jaw in a protrusive position relative to the upper jaw throughout the treatment period.

Advantages: No compliance requirement; forces are applied continuously, which can make treatment more efficient and predictable in patients who may struggle with the discipline required for removable appliance wear.

Considerations: There is typically a short adjustment period during which speech and eating feel unfamiliar. Fixed functional appliances are not removable for sport, which is a consideration for contact sport participants.

The choice between removable and fixed functional appliances is made based on the nature of the case, the degree of correction required, and an honest assessment of the individual patient’s likely compliance — all of which are discussed at the planning stage.

What Functional Appliances Can Correct

Functional appliances are primarily used to treat skeletal class II cases, where the lower jaw is underdeveloped or set back relative to the upper jaw. This typically presents as:

• Prominent upper front teeth with a large horizontal gap between upper and lower teeth (overjet)
• A deep overbite, where the upper front teeth cover a significant portion of the lower front teeth
• A recessed lower jaw and chin affect the facial profile
• A ‘gummy’ appearance of the upper teeth due to the lower jaw position

By guiding the lower jaw forward during growth, functional appliances reduce the overjet, improve the overbite, and create a more balanced jaw relationship and facial profile. In most cases, a phase of fixed brace treatment follows functional appliance therapy to finalise tooth alignment and the bite.

What Happens After Functional Appliance Treatment?

Functional appliance treatment is typically the first phase of a two-phase treatment plan. Once the jaw relationship has been improved, fixed braces — or in suitable cases, clear aligners — are used to align the teeth precisely within the corrected jaw framework. This second phase is usually shorter and more straightforward than it would have been without the prior jaw guidance.

Book a Consultation

To find out whether functional appliance treatment is appropriate for your teenager, book a specialist assessment at Lusk Orthodontics.