Functional Appliances

Creating a properly-aligned bite

Functional appliances are devices used to correct a significant disharmony in the relationship between the upper and lower jaws. They work by influencing the growth and development of the jaw of a young patient. The most common use of a functional appliance is to encourage the forward growth of a retrusive or under-developed lower jaw. The functional appliance holds the lower jaw forward over a period of time, until the teeth, jaws, and joints have adapted and the desired jaw position has been obtained.

The effectiveness of a functional appliance depends on:
  • How often the appliance is worn
  • How quickly the patient is growing
  • What the genetic basis of the patient is


Functional appliances can be used with braces or used alone

Functional appliances are typically used when the retrusion of the lower jaw is very severe (small lower jaw and prominent upper teeth commonly referred to as an overbite). The functional appliance plate is used to improve the lower jaw position relative to the upper jaw, then braces are placed on the teeth later. The movement of the jaw from being treated by the functional appliance improves the final result of the braces.

A properly-aligned bite helps create a beautiful smile

Functional appliances align the jaws not the teeth, so they are usually used as a first stage of orthodontic treatment, specifically for a young patient whose jaw is still growing and who has significant jaw disharmony. The second stage of treatment is the alignment of the teeth with fixed appliances (braces). The final result is a properly-aligned bite and straight teeth, which help maintain proper chewing, clear speech, and excellent oral health.

Removable Functional Appliances e.g. Twin Block, Andresen

Twin Block and Andresen appliances are easy to use and removable. The twin block comes in 2 parts – one made for the upper jaw and one made for the lower jaw. When worn together, they cause the lower jaw to be postured. The Andresen is a single appliance (monoblock) made for the upper jaw but again causes the lower jaw to bite in a forwards position.

Functional appliance treatment normally lasts approximately 9-24 months and is usually followed by fixed braces to get a perfect result.

Functional appliances rely on favourable jaw growth, wear and genetics for their success.

Treatment is typically started between the ages of 9 to 12 years to obtain the best results. Dr Hanks has his patients wear the functional appliance 12-14 hours a day and so there is no requirement to wear during the day / at school.

If there is poor cooperation or progress is not favorable due to adverse growth other treatment options may need to be considered in addition to fixed braces such as tooth extractions, or jaw surgery.