You usually think about your jaw as being solid like a rock, but when you are growing your jaw is really more like clay. If you apply pressure to your jaw, you can get your jaw to stretch. If you pull your jaw apart, your jaw will get wider. If you push your jaw back, your jaw will slowly move back. Your jaw does not actually stretch. Instead, when you pull on your jaw, your jaw grows in the direction you are pulling. Still, the important thing is that when your braces pull on your jaw, the braces change the shape of your jaw. In the same way, if you push on your teeth, your teeth will move around in your mouth. This is how orthodontics works.
The orthodontist pushes your jaw to stretch your mouth so all your teeth fit. The orthodontist then pushes on your teeth so they are all in the proper places. If your top jaw is too small, your orthodontist can install a special gadget called a “palatal expander” to get your jaw to grow wider. If your teeth stick out, your orthodontist can install another gadget called a “facebow” to push your back teeth back. In that way, your orthodontist is able to move around individual teeth and expand your jaw so that all of your teeth fit correctly in your mouth.