Phase I treatment oftern considered "interceptive" or "preventive" treatment.
Phase I is treatment stated at an earlier age while childern have mixed dentition (baby and adult teeth). Begining treatment at an early age helps the orthodontist to work with tooth and jaw development while that patient is activly growing, usually between the ages of 7-10.
This type of treatment is generally indicated if there are crossbite problems, jaw relationship problems or growth abnormalities. Partial braces may be used in Phase I treatment but often are not used.
Early orthodontic treatment can sometimes avoid extraction of permanent teeth and may produce a more stable long-term result. Phase I treatment is typically lasts 12 to 18 months followed by a period of observation until all permanent teeth erupt. Most patients require Phase II (full braces) around age 11-13 to finish the correction of the bite problem.