Underbite is when the lower front teeth are in front of the upper front teeth.
Often, it is not so much a problem with the teeth as it is with the jaw structure. Underbite patients usually have either an under-developed upper jaw, an over-developed lower jaw or some combination of the two. In orthodontic terms, this jaw growth discrepancy is called a skeletal class III malocclusion and it usually runs in families. Precise measurements of cephalometric x-rays of the patient's face and skull like the one shown above can help the orthodontist understand the growth pattern and predict the effectiveness of treatment.
Early treatment is aimed at orthopedically enhancing jaw growth of the upper jaw and retarding growth of the lower jaw. This is typically accomplished using a reverse pull headgear that the child wears at night while sleeping.
An underdeveloped upper jaw that is not growing forward in harmony with the lower jaw will also often be under-developed in a transverse dimension as well. In other words, the upper jaw is too narrow. This can be seen as a crossbite of the posterior teeth with the upper back teeth biting on the wrong side of the bottom back teeth. In the image above, this can be seen on the right side (which is the patient's left side).
The narrowness if the upper jaw can also lead to crowding of the top teeth. In this case, there is not enough room for the new incisors to grow in correctly.
The panoramic x-ray shows the crowding of the lateral incisors that want to come in but are not because of the crowding.
After expansion of the upper jaw and braces on the top teeth, space was created for the teeth to be aligned.
Night-time wear of a reverse headgear allowed for the jaw growth to be modified and returned to normal.
Now he can't stop smiling....