Two-phase refers to two separate periods of orthodontic treatment that a child may receive. The first phase takes place when the child still has most of their baby teeth, and aims to fix easily corrected problems, with or without the use of braces. At this time other orthodontic appliances are usually used. Phase I takes care of initial structural correction so that braces can work better.
The second phase consist of full braces and is designed to finish straightening the teeth and correcting any jaw alignment issues.