For most patients, the best time to be treated orthodontically is after all of the permanent teeth erupt but BEFORE growth is complete. If all the permanent teeth are in, treatments are usually faster, more effective, and cheaper. There are a few exceptions (see For Children--Early Treatment).
It is usually best to begin treatment on girls by age 12 or 13. Because growth is such a large part of treatment, timing is critical to obtain the best result. The female growth spurt usually occurs 1 year prior to menarche (first period) and continues until about 1 year after. Just before or during this growth spurt is the best time to begin treatment. Some girls have completely finished their growth by age 14 so it is important to treat them a little earlier than boys.
Boys generally have a larger window of opportunity for treatment. While most boys complete the majority of their growth by 16 or 17, some boys continue to grow into their early 20's. For most boys, it is recommended to begin treatment by age 14 if significant growth correction is needed. For social reasons, it is nice to begin treatment at 12 or 13 if possible (to avoid braces as a Jr or Sr in high school).
Time in treatment depends on the severity of the problems and generally takes 1-2 yrs. For many patients, treatment time depends largely upon cooperation in keeping appointments, maintaining good oral hygiene, and compliance with elastic use.