Phase I orthodontics is limited treatment (i.e. expanders, retainers or partial braces) that occurs before all permanent teeth have erupted. Such treatment usually takes place between the ages of seven and ten. Phase I treatment is often recommended to make space for developing teeth; to correct crossbites, overbites and underbites; or to end harmful habits (such as thumb- sucking). Phase II treatment is also called “comprehensive treatment” because it involves full braces when all permanent teeth have erupted. This usually occurs between the ages of 11 and 13.