A normal upper jaw is formed when the tongue rests in the area between the upper teeth.
When the tongue is in this position, it counteracts the pressure of the cheeks. If the tongue is not maintained in the correct position the teeth move inward and create crooked teeth and a narrow jaw.
If the lips and tongue are not functioning correctly, the crowded teeth and jaws will then create a misaligned jaw and crooked teeth. If the jaw shape and function are not correct, there is insufficient room for teeth in the mouth.