A malocclusion is a misalignment or incorrect relation between the teeth of the two dental
arches when they approach each other as the jaws close.
The term was coined by Edward Angle, the "father of modern orthodontics", as a derivative of
occlusion, which refers to the manner in which opposing teeth meet.
Presentation Malocclusion is a common finding, although
it is not 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.
Such skeletal disharmonies often distort sufferer's face shape, severely affect aesthetics of
the face and may be coupled with mastication or speech problems.
Most skeletal malocclusions can only be treated by orthognathic surgery.
Classification Depending on the sagittal relations of teeth
and jaws, malocclusions can be divided mainly into three types according to Angle's classification
method.
However, there are also other conditions, e.g. crowding of teeth, not directly fitting
into this classification.
Many authors have tried to classify or modify Angle's classification.
This has resulted in many subtypes.
Angle's classification method
Edward Angle, who is considered the father of modern orthodontics, was the first 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 align with the
buccal groove of the mandibular first molar.
The teeth should all fit on a line of occlusion which, in the upper arch, is a smooth curve
through the central fossae of the posterior teeth and cingulum of the canines and incisors,
and in the lower arch, is a smooth curve through the buccal cusps of the posterior teeth and
incisal edges of the anterior teeth.
Any variations from this resulted in malocclusion types.
It is also possible to have different classes of malocclusion on left and right sides.
Class I: Neutrocclusion Here the molar relationship of the occlusion is normal or as described
for the maxillary first molar, but the other teeth have problems like spacing, crowding,
over or under eruption, etc.
Class II: Distocclusion In this situation, the mesiobuccal cusp of the upper first molar
is not aligned with the mesiobuccal groove of the lower first molar.
Instead it is anterior to it.
Usually the mesiobuccal 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.
Class III: Mesiocclusion In this case the upper molars are placed not in the mesiobuccal
groove but posteriorly to it.
The mesiobuccal cusp of the maxillary first molar lies posteriorly to the mesiobuccal
groove of the mandibular first molar.
Usually seen as when the lower front teeth are more prominent than the upper front teeth.
In this case the patient very often has a large mandible or a short maxillary bone.
Crowding of teeth Crowding of teeth is where there is insufficient
room for the normal complement of adult teeth.
Causes Extra teeth, lost teeth, impacted teeth, or
abnormally shaped teeth have been cited as causes of malocclusion.
A small underdeveloped jaw, caused by lack of masticatory stress during childhood, can
cause tooth overcrowding.
Ill-fitting dental fillings, crowns, appliances, retainers, or braces as well as misalignment
of jaw fractures after a severe injury are other causes.
Tumors of the mouth and jaw, thumb sucking, tongue thrusting, pacifier use beyond age
3, and prolonged use of a bottle have also been identified as causes.
In an experiment on two groups of rock hyraxes fed hardened or softened versions of the same
foods, the animals fed softer food had significantly narrower and shorter faces and thinner and
shorter mandibles than animals fed hard food.
Experiments have shown similar results in other animals, including primates, supporting
the theory that masticatory stress during childhood affects jaw development.
Only one small study has investigated this effect in humans.
Children chewed a hard resinous gum for two hours a day and showed increased facial growth.
A 2011 paper suggested that "the changes in human skulls are more likely driven by the
decreasing bite forces required to chew the processed foods eaten once humans switched
to growing different types of cereals, milking and herding animals about 10,000 years ago."
Treatment Crowding of the teeth is treated with orthodontics,
often with tooth extraction, Invisalign, or dental braces, followed by growth modification
in children or jaw surgery in adults.
Surgery may be required on rare occasions.
This may include surgical reshaping to lengthen or shorten the jaw.
Wires, plates, or screws may be used to secure the jaw bone, in a manner similar to the surgical
stabilization of jaw fractures.
Very few people have "perfect" alignment of their teeth.
However, most problems are very minor and do not require treatment.
Other conditions
Other kinds of malocclusions are due to vertical discrepancies.
Long faces may lead to open bite, while short faces can be coupled to a deep bite.
However, there are many other more common causes for open bites, and likewise for deep
bites.
Malocclusions can also be secondary to transverse skeletal discrepancy or to a skeletal asymmetry.
Etiology Oral habits and pressure on teeth or the maxilla
and mandible are etiological factors in malocclusion.
In the active skeletal growth, mouthbreathing, finger sucking, thumb sucking, pacifier sucking,
onychophagia, dermatophagia, pen biting, pencil biting, abnormal posture, deglutition disorders
and other habits greatly influence the development of the face and dental arches.
Pacifier sucking habits are also correlated with otitis media.
Dental caries, periapical inflammation and tooth loss in the deciduous teeth alter the
correct permanent teeth eruptions.
See also Maximum intercuspation
Occlusion References