Phase I, or early interceptive treatment, is limited orthodontic treatment before all of the permanent teeth have erupted. This treatment typically occurs between the ages of 6 and 10 and may be recommended to:
Make more space for developing teeth
Adjust crossbites, overbites, and underbites
Correct harmful oral habits
Phase II treatment, or comprehensive treatment, involves full braces when all permanent teeth have erupted, usually between the ages of 11 and 13.