The American Association of Orthodontists recommend that your child have an orthodontic consultation at age 7. The reason for this consultation is to identify certain problems that may require early intervention to avoid lengthy treatments at a later date. Early treatment in children is only indicated for a very few bite problems. These include cross-bites, under-bite, insufficient space for the permanent teeth to come in the mouth and extremely protrusive upper front teeth (buck teeth). Frequently used appliances at an early age are expanders, and appliances to either maintain or regain space. These early interventions are important since they lead to better outcome as the face and teeth develop.
Because the position of the teeth is closely related to the position and size of the jaws, treatment should be initiated prior to facial growth completion and preferably prior to puberty so the natural growth can be utilized to change the jaws and along with it the teeth. The start of puberty for girls is 11 to 12 and for boys 12-13 on average. Once growth is completed the jaw position can not be corrected unless surgery is used along with braces.
The duration of treatment depends on age at start and the complexity of your bite. On average it ranges from 12 months to 24 months, with most cases being 18 months. The most important factor in duration and outcome of treatment lies with you. Following instructions will result in the best outcome and avoid extending treatment duration.
You may also read through the brochure written by AAO on Two Phase Orthodontic Treatment which describes the appropriate treatment at the appropriate time.