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A malocclusion refers to the misalignment of teeth and/or incorrect relation between the teeth of the two dental arches. The upper arch is called the maxilla and the lower is called the mandible.

Most people have some degree of malocclusion, although it isn't usually serious enough to require treatment. Those who have more severe malocclusions may require orthodontic and sometimes surgical treatment to correct the problem. Correction of malocclusion may reduce risk of tooth decay and help relieve excessive pressure on the temporomandibular joint. Orthodontic treatment is also used to align for aesthetic reasons.

Malocclusions may be coupled with skeletal disharmony of the face, where the relations between the upper and lower jaws are not appropriate. In these cases the dental problem is, most of the time, derived from the skeletal disharmony.

Malocclusions can be divided mainly into three types, depending on the sagittal relations of teeth and jaws:

Edward Hartley Angle, who is considered the father of modern orthodontics, was the first one to classify malocclusion. He based his classifications on the relative position of the maxillary first molar. According to Angle, the mesiobuccal cusp of the upper first molar should rest on the mesiobuccal groove of the mandibular first molar. Any variations from this resulted in malocclusion types. It is also possible to have different classes of maloclusion on left and right sides.

• Class I: Here the molar relationship of the occlusion is normal or as described before, but the other teeth have problems like spacing, crowding, over or under eruption, etc.

• Class II: In this situation, the upper molars are placed not in the mesiobuccal groove but anteriorly to it. Usually in the mesio buccal cusp rests in between the first mandibular molars and second premolars.

there are two subtypes

• Class II Division 1: The molar relationships are like that of Class II and the anterior teeth are protruded.

• Class II Division 2: The molar relationships are class II but the central are retroclined and the lateral teeth are seen overlapping the centrals. Here the retroclined central

• Class III: (prognathism or negative overjet) is when the lower front teeth are more prominent than the upper front teeth. In this case the patient has very often a large mandible or a short maxillary bone.

Other kind of malocclusions are due to vertical discrepancies. Long faces may lead to open bite, while short faces can be coupled to a deep bite. Although there are many other more common causes for open bites such as tongue thrusting, thumb sucking, etc, and likewise for deep bites.

Malocclusions can also be secondary to transversal skeletal discrepancy or to a skeletal asymmetry.

Many authors have tried to classify or modify Angle's classification. This has resulted in many subtypes.

• Slideshow (in French, but many illustrations)