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Glossary of Orthodontic Terms
A
Alveolus
The bone surrounding each tooth

Ankylosis
An abnormal union between two bones or between a root surface and surrounding bone resulting in tooth immobility.

Anterior open bite
The lower incisors are not overlapped in the vertical plane by the upper incisors and do not occlude with them.

Archwire
A wire engaged into orthodontic brackets which delivers a force to produce tooth movement.

Articulator

An instrument that mimics the movements of the lower jaw to which individual patients upper and lower dental study models can be attached.

B
Bilateral sagittal split osteotomy
A surgical procedure to reposition the lower jaw forwards, backwards or by rotation.

Bimaxillary
Relating to the upper an lower dental arches or jaws.

Bimaxillary surgery
Surgery to reposition both upper and lower jaws.

Bracket
A precisely fabricated fixed orthodontic attachment made from metal, ceramic or plastic that is bonded to the teeth.

Buccal
In the direction of the cheeks.

C
Class 1 incisor relationship
The lower incisors bite 2-4 mm behind the upper incisors.

Class 2 division 1 incisor relationship
The lower incisors bite further behind the upper incisors than normal and the upper incisors are normally inclined or proclined.

Class 2 division 2 incisor relationship
The lower incisors bite further behind the upper incisors then normal and the upper incisors are retroclined.

Class 3 incisor relationship
The lower incisor bite further forwards of the upper incisors than normal.

Complete overbite
An overbite in which the lower incisors make contact with either the upper incisors or the gum tissue in the roof of the mouth.

Craniosynostosis
A birth defect that may occur as an isolated phenomenon or as part of a syndrome, consisting of premature fusion of one or more skull sutures.

Crossbite
The upper incisor teeth or upper molar teeth bite on the inside on the lower teeth.

D
Decalcification
Often used to describe the loss of mineral from the tooth surface immediately surrounding an orthodontic appliance. It is caused by excessive intake of sugar and accumulation of bacteria (plaque) on the tooth surface. It results in permanent discolouration of the tooth surface and cavitation if extreme.

Decompensation
The process of removing dental compensations, using fixed appliances, that have attempted to naturally compensate for a mismatch in the jaw relationship. Decompensation is often carried out prior to surgical correction of jaw relationships.

Dental arch
The arch formed by the upper and lower teeth when viewed from below or above respectively.

Dento-alveolar compensation
The inclination of the teeth is naturally altered to help compensate for a mismatch in the jaw relationship.

Diastema
A space between teeth (most commonly the upper central incisors).

Distal
Away from the midline.

Distraction osteogenesis
A surgical technique for lengthening bones.

E
Ectopic eruption
The eruption of a tooth in an abnormal position.

Expansion appliance
An orthodontic appliance used commonly to increase the width of the upper dental arch or jaw.

F
Fixed appliance
An appliance that is fixed to the tooth surfaces in order to produce tooth movement.

Frenum
A fold of mucous membrane

G
Genioplasty
A surgical procedure to reposition the chin.

Gingiva
The gum tissue surrounding teeth.

Gingival recession
A shift of the gum margin exposing the root surface.

Graft
Any material or tissue that is not normally part of an organ or tissue, implanted or transplanted for the purpose of reconstruction or repair.

H
Hypodontia
The developmental absence of teeth excluding the wisdom teeth.

I
Implant
An artificial material that is placed into the body. Often used to refer to dental implants.

Impression
An imprint of the upper and/or lower teeth used to make study models of the teeth.

Incompetent lips
With the lower jaw in the rest position the lips are apart and muscular effort is required to obtain a lip seal.

Inferior alveolar nerve
A nerve which travels in the inferior dental canal (see below) and supplies sensation to the lower teeth, the lower gum tissue and the skin covering the lower lip and chin.

Inferior dental canal
A canal that runs in the lower jaw that contains the inferior alveolar (dental) nerve (see inferior alveolar nerve).

Infraocclusion
A situation in which a tooth or group of teeth are positioned below the level of adjacent teeth commonly due to ankylosis (see ‘ankylosis’).

L
Labial segments

The segment of the jaw containing the incisor teeth.

Labiomental sulcus
The groove created where the curvature of the lower lip merges with the skin overlying the lower lip.

Lateral Cephalogram
A radiograph of the side of the face and skull taken in a standardised reproducible position allowing accurate comparisons between radiographs taken at different time points.

Le Fort 1 osteotomy
A surgical procedure of the tooth bearing segment of the upper jaw used to reposition the jaw most commonly in an anterior, upward (impaction) or downward direction.

Lingual arch
A form of fixed orthodontic appliance that runs between the inner surfaces of the lower molar teeth designed to help prevent forward movement of the molars.

M
Malocclusion
A poor relationship between the upper and lower dental arches or abnormal tooth positions.

Mandible
The lower jaw.

Maxilla
The upper jaw.

Maxillary antrum
The a chamber present in the upper jaw and closely associated with the roots of the upper molar teeth.

Mesial
Towards the midline.

Micrognathia
Abnormally small jaw size.

N
Nance palatal arch
A form of fixed orthodontic appliance that runs between the inner surfaces of the upper molar teeth designed to help prevent forward movement of the molars.

Nasolabial angle
The angle formed by the junction of the nasal base and upper lip.

O
Orbital hypertelorism
An greater than normal distance between the inside walls of the orbital cavities.

Orbital hypotelorism
A reduced distance between the inside walls of the orbital cavities.

Osteotomy
Surgical procedure involving cutting the bone.

Overbite
The overlap of the lower incisors by the upper incisors in the vertical plane.

Overjet
The distance between the front surface of the lower incisors and the front surface of the upper incisors. The front surface of the upper incisors is usually 2-4 mm ahead of the front surface of the lower incisors.

P
Paresthesia
Diminished or abnormal sensation, such as burning, prickling, tingling or numbness.

Plaque
A soft, thin film of adherent deposit on the tooth surface composed of bacteria, bacterial products and salivary constituents. Some bacteria within plaque are associated with dental decay and gum disease.

Pogonion
The most anterior point on the contour of the chin.

Proclined
The upper or lower incisors are inclined forwards to a greater degree than normal.

Prognathism
Protrusion of the jaw, most commonly the lower.

Q
Quad helix appliance
A form of expansion appliance that partially covers the roof of the mouth.

R
Retainer
An orthodontic appliance used following orthodontic treatment in order to maintain the corrected tooth positions whilst the surrounding bone and gum tissue adapt to the new positions.

Retroclined
The upper or lower incisors are inclined backwards to a greater degree than normal.

Retrognathism
Retrusion of the jaw. Often used to refer to the upper and lower jaw.

Root resorption
Loss of root length often accompanying orthodontic treatment.

S
Scissor bite
One or more of the upper molar teeth bite outside to the lower molar teeth.

Skeletal Pattern
The relationship between the dental arches in the anterior-posterior plane.

Supernumerary teeth
Teeth in excess of the usual number.

Study models
Casts of the upper and lower teeth used to plan and monitor treatment changes.