Malocclusion is a term that refers to an abnormal alignment of the upper and lower teeth. When the teeth are abnormally aligned, dental problems, such as difficulty with biting or chewing, can occur. Malocclusion can also make the face look unnatural, cause a person to breathe through the mouth, and create problems with speech. In severe cases, untreated malocclusion can lead to extreme stress on, and eventual damage to, the affected teeth.

Nearly 90 percent of children have some degree of malocclusion, although only a small percentage will require orthodontic treatment.

Types of Malocclusion

There are several types of malocclusion, any of which may necessitate orthodontic treatment. Malocclusion is divided into three classes: Class I, in which teeth are overcrowded in spite of proper alignment of the upper and lower jaws; Class II, in which the lower molars fit the upper molars, but are located toward the throat, pulling the chin back; and Class III, in which the lower molars are too far forward to fit with their corresponding upper molars, creating a jutting jaw.

Upper Protrusion

In a patient with upper protrusion, the upper-front teeth push outward (often referred to as "buck teeth"). Causes of upper protrusion include an unusually small lower jaw. Thumb-sucking or pacifier use may also result in, or exacerbate, upper protrusion.


In a patient with an overbite, the upper-front teeth extend abnormally far down over the lower-front teeth. In extreme cases, this can cause the lower teeth to bite into the roof of the mouth.


In a patient with an underbite, the lower-front teeth extend farther forward than the upper-front teeth, resulting in an irregular bite, and an abnormal appearance.


A crossbite occurs when some or all of the upper teeth misalign with the lower teeth, so that the upper and lower teeth meet incorrectly.

Open Bite

In a patient with an open bite, the upper- and lower-front teeth do not overlap completely, so that, even when the mouth is closed, there is an opening between the upper and lower teeth.

Causes of Malocclusion

In most cases, malocclusion is hereditary. Other causes of malocclusion include the following:

  • Birth defects, such as cleft palate
  • Thumb-sucking
  • Prolonged use of bottle or pacifier
  • Tooth loss; excessive number of teeth; abnormally shaped teeth
  • Misalignment of jaw due to traumatic injury

Although for most patients malocclusion is only a cosmetic concern, for some it may be disfiguring, and result in problems with speaking or eating. In those cases, malocclusion can usually be corrected with orthodontic treatment.

Treatment of Malocclusion

Treatment for malocclusion varies depending on the severity of the problem, and the age of the patient. Most cases can be treated by some combination of the following:

  • Extraction of unnecessary teeth
  • Repair or reshaping of irregular teeth
  • Bonding or crowning of teeth
  • Attaching braces to the teeth to correct misalignment
  • Orthognathic surgery, in severe cases, to reshape the jaw

Braces are typically worn for 1 to 2 years, followed by the wearing of a nighttime retainer to hold the teeth in the corrected position. The goals of orthodontic treatment for malocclusion are to improve appearance, make cleaning the teeth easier to decrease the risk of decay and periodontal disease, and to eliminate strain on the jaw and teeth. Such treatment may also protect teeth from possible loosening or fracture, and reduce symptoms of temporomandibular joint disorder (TMD).

Additional Resources