The forces exerted by the lips and the tongue primarily influence the growth of a child’s face. The lips and cheeks exert an inward pressure on the face, with the tongue providing a counteracting force. When the mouth is closed, the tongue rests against the roof of the mouth, exerting light forces that shape the top jaw. Because the tongue is wide and U-shaped, it follows that the shape of the top jaw should be wide and U-shaped also. In other words, the shape of the top jaw reflects the shape of the tongue. A wide U-shaped top jaw is optimal for housing all our teeth.
