Malocclusion means the teeth are not aligned properly.

Occlusion refers to the alignment of teeth and the way that the upper and lower teeth fit together (bite). Ideally, all upper teeth fit slightly over the lower teeth. The points of the molars fit the grooves of the opposite molar.

The upper teeth keep the cheeks and lips from being bitten and the lower teeth protect the tongue.

Malocclusion is most often hereditary, which means the condition is passed down through families. There may be a difference between the size of the upper and lower jaws or between jaw and tooth size, resulting in overcrowding of teeth or in abnormal bite patterns.

Variations in size or structure of either jaw may affect its shape, as can birth defects such as cleft lip and palate. Other causes of malocclusion include:

• Childhood habits such as thumb sucking, tongue thrusting, pacifier use beyond age 3, and prolonged use of a bottle
• Extra teeth, lost teeth, impacted teeth, or abnormally shaped teeth
• Ill-fitting dental fillings, crowns, appliances, retainers, or braces
• Misalignment of jaw fractures after a severe injury
• Tumors of the mouth and jaw

There are different categories of malocclusion.

• Class 1 malocclusion is the most common. The bite is normal, but the upper teeth slightly overlap the lower teeth.
• Class 2 malocclusion, called retrognathism or overbite, occurs when the upper jaw and teeth severely overlap the bottom jaw and teeth.
• Class 3 malocclusion, called prognathism or underbite, occurs when the lower jaw protrudes or juts forward, causing the lower jaw and teeth to overlap the upper jaw and teeth.

• Abnormal alignment of teeth
• Abnormal appearance of the face
• Difficulty or discomfort when biting or chewing
• Speech difficulties (rare) including lisp
• Mouth breathing (breathing through the mouth without closing the lips)

Most problems with teeth alignment are discovered by a dentist during a routine exam. The dentist may pull your cheek outward and ask you to bite down to check how well your back teeth come together. If there is any problem, the dentist will usually refer you to an orthodontist for diagnosis and treatment.

Dental x-rays, head or skull x-rays, or facial x-rays may be required. Plaster or plastic molds of the teeth are often needed.

Very few people have perfect teeth alignment. However, most problems are so minor that they do not require treatment.

Malocclusion is the most common reason for referral to an orthodontist.

By treating moderate or severe malocclusion, the teeth are easier to clean and there is less risk of tooth decay and periodontal diseases (gingivitis or periodontitis). Treatment eliminates strain on the teeth, jaws, and muscles, which lessens the risk of breaking a tooth and may reduce symptoms of temporomandibular joint disorders.

The goal is to correct the positioning of the teeth. Braces or other appliances may be used. Metal bands are placed around some teeth, or metal, ceramic, or plastic bonds are attached to the surface of the teeth. Wires or springs apply force to the teeth.

One or more teeth may need to be removed if overcrowding is part of the problem. Rough or irregular teeth may be adjusted down, reshaped, and bonded or capped. Misshapen restorations and dental appliances should be repaired. Surgery may be required on rare occasions. This may include surgical reshaping to lengthen or shorten the jaw (orthognathic surgery). Wires, plates, or screws may be used to stabilize the jaw bone, in a similar manner to the surgical stabilization of jaw fracture.

It is important to brush and floss your teeth every day and have regular visits to a general dentist. Plaque accumulates on braces and may permanently mark teeth or cause tooth decay if not properly cared for.

Retainers (used to stabilize the teeth) may be required for an indefinite time to maintain the new position of the teeth.

Problems with teeth alignment are easier, quicker, and less expensive to treat when they are corrected early. Treatment is most successful in children and adolescents because their bone is still soft and teeth are moved more easily. Treatment may last 6 months to 2 or more years, depending on the severity of the case.

Treatment of orthodontic disorders in adults is often successful but may require longer use of braces or other devices.

• Tooth decay
• Discomfort during treatment
• Irritation of mouth and gums (gingivitis) caused by appliances
• Chewing or speaking difficulty during treatment

Call your orthodontist if toothache, mouth pain, or other new symptoms develop during orthodontic treatment.

Many types of malocclusion are not preventable. Control of habits such as thumb sucking may be necessary in some cases. However, early detection and treatment may optimize the time and method of treatment needed.