This is a term that refers to childhood or adolescents receiving orthodontic care. The two phases are called Early Interceptive Treatment and Comprehensive Orthodontic Treatment, respectively.

Phase I typically takes place between the ages of 6 and 10, is of one year duration or less and is limited to adjustments deemed necessary to discourage early life habits like thumb-sucking and ensure optimal placement of arriving adult teeth.

Phase II usually begins only after the permanent adult teeth have arrived (often between the ages of 11 and 13).