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 opposing molar. All teeth are aligned, straight, and spaced proportionally. The upper teeth keep the cheeks and lips from being bitten and the lower teeth protect the tongue.

Malocclusion is the most common reason for referral to an orthodontist. Very few people have perfect occlusion. However, most occlusion problems are so minor that they do not require treatment.

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 reduces symptoms of temporomandibular joint disorders.

Malocclusion is most often hereditary. There may be a disproportion 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. Extra teeth, malformed teeth, impacted or lost teeth, and teeth that erupt in an abnormal direction may contribute to malocclusion. Variations in size or malformation of either jaw may affect its shape, as can birth defects such as cleft lip and palate.

During infancy, personal habits like thumb sucking, tongue thrusting, pacifier use beyond the age of three, and prolonged use of a bottle can greatly affect the shape of the jaws as well. The improper fit of dental fillings, crowns, appliances, retainers or braces may contribute to malocclusion. Misalignment of jaw fractures after a severe injury, and tumors of the mouth or jaw may cause malocclusion as well.

• 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.