About three to five percent of the population has a lower jaw that is to some degree longer than the upper jaw. This can cause the lower front teeth to protrude ahead of the upper front teeth, creating a crossbite. Careful monitoring of jaw growth and tooth development is indicated for these patients.
This type of problem can also lead to headaches, speech problems, and stomach upsets due to poor chewing efficiency; it also causes the lower lip to protrude, giving the face a look of anger or displeasure even when the patient is noticeably happy. Treatment for this problem will improve facial appearance.