A tongue placed in the right position can do a lot of shaping of the mouth, jaw, and face. Mouth breathing during the day and while sleeping can cause it to not be in the correct position.
Fact: The tongue has the strongest muscles in the body and can exert up to 500g (17.5oz) of force. It only takes 1,7g (0.05oz) of force to move an individual tooth.
When you aren't eating or talking, your tongue should rest on the roof of your mouth. This is because the tongue position determines the shape and size of the upper jaw. If your child habitually mouth breathes or has a tongue tie, the upper teeth will not have enough space and the chin will be forced back and down.
A normal top jaw grows properly because the tongue rests in the correct position (known as the Correct Tongue Resting Position), which is in the roof of your mouth. If your tongue does not rest on the roof of your mouth, your upper jaw may become too narrow. This means that there won't be enough room for teeth to grow and be straight.