Functional appliances

Functional appliances (e.g. the Twin Block) are a popular type of reducing the projection of the front teeth in patients who are growing.

What is a functional appliance?

A functional appliance is a type of brace to correct a "Class II" problem; Class II problems are a group of bite problems where the top teeth bite in front of the lower teeth. Functional appliances may be either fixed or removable. Removable functional appliances are most popular in the U.K. The more common removable functional appliances are made from separate upper and lower parts, which interlock placing the lower jaw in a more advanced position. Other types of functional appliance are made from just one piece, although these may adapt slightly less well to the teeth.

Are there alternative to functional braces?

There are; however, correction of prominent top teeth (Class II) is not straightforward and relies on co-operation from you or your child. Simply placing train track braces is usually insufficient as fixed braces (train tracks) are designed primarily to straighten teeth. Consequently, to address both Class II problems and crooked teeth may require the use of both a functional appliance, followed by fixed braces or less commonly use of functional and fixed braces together. Alternatives to a functional appliance may include a head brace or extractions; however, the indications for each approach depends on the specific problem.

Will a functional brace change the shape of the face?

Much debate and controversy has surrounded the mode of action of functional braces. It appears that functional braces primarily tip teeth, moving top teeth backwards and lower teeth forwards. Reliable research suggests that the position and length of the lower jaw is governed by our genetic make-up. Therefore, while growth of the lower jaw may be altered in the short-term by a functional brace, it appears that in the long-term no significant difference in jaw position is likely to occur. Nevertheless, by virtue of moving the teeth, changes in lip position may occur with the upper lip covering the top teeth more fully.

Is treatment with functional braces always successful?

Not necessarily. Obviously, treatment will not work if the appliance is not worn sufficiently well. In addition, there are a group of patients who do not respond particularly well to functional braces. Unfortunately, it is very difficult to predict which patients will respond to treatment. Functional appliances are believed to be most successful prior to or during the adolescent growth spurt. This typically occurs between the ages of 11 and 14 in boys and 10 to 13 in girls. Nevertheless, treatment may be suggested at an earlier or later stage in certain circumstances.

If treatment is unsuccessful, how can the problem be addressed?

Class II problems may be treated in a variety of ways. If Class II correction fails, a variety of options exist. Consideration may be given to using an alternative device or approach to correct the Class II including:

• Headgear
• Extractions
• Jaw surgery

The indications for these approaches vary and is based on the specific problem. In certain instances it may be advisable to accept the residual problem before considering treatment if desired at a later date. Jaw surgery is generally deferred until 17 years and above.

Is there any benefit in using functional appliances before the age of 10 years?

Treatment in this age group is regarded as ‘early treatment’ in the U.K. although this practice is routine in many countries. Research has demonstrated that functional appliance therapy commenced at an early stage is no more effective but is less efficient than treatment commenced at 10 to 14 years. In certain circumstances, however, particularly if children are the subject of teasing in relation to dental appearance, early treatment may be recommended.

How long will treatment take?

Treatment time varies based on how severe the problem is. However, most of the work with this brace is usually completed in 9 to 12 months. After this a period of nights only wear may be advised to maintain the improvement. However, progression to a second phase of treatment with a train track brace may be recommended immediately.

How much do I need to wear the brace? 

The number of hours per day that you are expected to wear the brace will be explained to you. For the treatment to work it is important you follow these instructions. However, most functional appliances are worn on a full-time or near full-time basis. With the correct number of hours of wear you may find the improvement in the position of your teeth can be quite dramatic.