Teeth protrusion is a common problem around the world that may result from one of more of the following reasons:
1- Protrusion of the upper jaw, or the backward retrusion of the lower jaw, or because of both.
2- The protrusion of the upper front teeth, or the backward retrusion of the lower front teeth, or because of both.
3- A mixture of the previous problems together. 

Functional orthodontics is a type of orthodontic treatment used for children aged between 10 and 13 years. It encourages and directs the growth of the lower jaw in forwarding direction, which represents the solution of protrusion.

Starting treatment at the right time is a decisive factor in its success, a child's pre-puberty period is very important because bone growth increases during it. At this age, functional orthodontic devices can direct the growth of the lower jaw forward, and there are several theories (which many scientists do not agree with) indicate the ability of these devices to stimulate further growth.
There are several forms and types of these devices, but here I will mention only two types (the most widespread ones):

1- Removable functional device
A device manufactured in dental laboratories, and designed to force the lower jaw to move forward and directs its growth in the appropriate direction. It is necessary to wear the device for at least 18 hours a day, that's why child's cooperation and commitment is very necessary, this treatment lasts between 6-12 months, after reaching the appropriate protrusion, fixed braces are often used to align the teeth and reach the ideal occlusion.

2- Fixed functional device.
One of the disadvantages of the previous type - the functional movable orthodontics - is the necessity of patient's commitment, which may not always be guaranteed, in addition to the long treatment period which is divided to two treatment stages (the functional device stage and the fixed braces stage), so this type is more practical solution for the both problems, we do not need child's commitment because the device is fixed to the teeth, and the treatment period is shorter because the fixed braces is installed and combined with the functional device.
At the beginning, the fixed orthodontic braces is bonded on teeth, and after a while, the functional device - which is metal tubes or springs - is installed on the wires or other parts of the fixed orthodontic. The patient wears functional orthodontics for several months, after which he removes it but keeps using the fixed braces until the end of the treatment.
 

This type of orthodontic treatment - if applied at the right time and for the appropriate cases - is a good alternative to more severe and longer treatments such as Orthognathic surgery, or even tooth extraction.
In some cases, this orthodontic improves the child's facial profile, as we note in the following case.