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Malocclusion

Also called: Crooked Teeth, Dental Malocclusion, Misaligned Teeth

- Summary
- About malocclusion
- Types and differences
- Potential causes
- Signs and symptoms
- Diagnosis methods
- Treatment options
- Questions for your doctor

Reviewed By:
Kenneth Cheng, D.D.S.

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Types and differences of malocclusion

Although various abnormalities can cause malocclusion, most conditions can be grouped according to one of three categories. They are:

Class I. Occurs when the bite is normal but the teeth may still be crowded or otherwise malpositioned. It is the most common form of malocclusion.
Class II. Occurs when the upper jaw and teeth overlap the bottom jaw and teeth. Also called retrognathism or overbite.
Class III. Occurs when the lower jaw protrudes forward and the lower teeth extend over the upper teeth. Also called prognathism or underbite.

Potential causes of malocclusion

In most cases, the source of a malocclusion is developmental. A person may have malocclusion if the upper and lower jaw are not the same size. Or, malocclusion may result if a person’s mouth is especially small, causing teeth to become crowded and to shift out of position. Malformed teeth, impacted teeth and teeth that erupt in an abnormal fashion can all cause malocclusion.

In addition, nearly 25 percent of craniofacial abnormalities that affect oral development are associated with mental retardation, according to the National Institutes of Health. These problems can include malocclusion, extra or malformed teeth and developmental tooth defects. Genetic conditions that cause cerebral palsy and cleft palate also are likely to result in bite problems.

However, other malocclusions can be acquired through certain situations, including:

Trauma. Teeth that are fractured or knocked out and reimplanted may fuse with the bone around them (ankylosis) following replacement. This prevents the teeth from lining up properly in the jaw of growing children, resulting in an irregular bite.
Illnesses and other problems. Dental disease and problems that develop after birth (e.g., air obstruction by tonsils and adenoids) can cause malocclusions. Tumors of the mouth or jaw also can cause malocclusion.
Problems associated with dental restorations. Improper fit of certain types of dental work can cause malocclusion. These include fillings, crowns, appliances, retainers or braces. Misalignment of jaw fractures following a severe injury also can cause malocclusion.
Prolonged thumb sucking or use of a pacifier. Children who engage in either of these habits after their permanent teeth erupt about age 6 or 7 can force the upper teeth to protrude over the lower teeth. Thumb sucking and pacifier use in younger children may not significantly increase the risk of malocclusion.
Premature loss of baby teeth. When a primary tooth is lost too early, it can cause the emerging permanent tooth to drift or erupt incorrectly. Some primary teeth are lost due to tooth decay. In certain cases, adjacent primary teeth may move into the gap left by the tooth that was lost early. This can prevent the permanent tooth from coming in.
Tongue-thrusting. A long-term habit of pushing the tongue onto the back of the front teeth during swallowing can cause the teeth to protrude.