Learning - Glossary

ANCHORAGE

The resistance to forces generated in reaction to the active components of an appliance. This is the resistance of unwanted tooth movements.

ANTERIOR OPEN BITE

Lack of vertical overlap of the incisors when the buccal segment teeth are in occlusion.

ARCH FORM

The shape of the mandibular or maxillary arch.

ARCHWIRE

A wire engaged in the brackets of a fixed appliance that generates active forces for tooth movement and alignment.

BIMAXILLARY PROCLINATION

When upper and lower incisors are proclined relative to the mandible/maxilla.

BODILY MOVEMENT

Equal movement of the root and crown of a tooth in the same direction. Occurs during space closure in comprehensive orthodontic treatment, when using large dimension rectangular steel wires.

BOLTON (TOOTH SIZE) DISCREPANCY

Variation from the normal ratio between the sum of the mesiodistal widths of the maxillary and mandibular dentition. This makes it difficult to achieve an ideal occlusal fit.

BUCCAL CROSSBITE

The buccal cusps of the lower premolars and/or molars occlude buccally to the buccal cusps of the upper premolars and/or molars.

BUCCAL SEGMENT

The canines, premolars and molars.

CEPHALOMETRY

Measurement of the bony structures of the head using reproducible lateral and anteroposterior radiographs. In comprehensive orthodontics a lateral cephalometric radiograph (lateral ceph/lateral skull) is often required.

CINGULUM PLATEAU

The convexity of the cervical third of the lingual/palatal aspect of the incisors and canines.

CLASS I INCISOR RELATIONSHIP

The lower incisor edges occlude on or directly beneath the cingulum plateau of the upper incisors (British Standards Institute classification).

CLASS I MOLAR RELATIONSHIP

The mesiobuccal cusp of the upper first molar lies in the buccal groove of the lower first molar.

CLASS II DIVISION 1 INCISOR RELATIONSHIP

The lower incisor edges lie posterior to the cingulum plateau of the upper incisors, the overjet is increased and the upper central incisors are normally inclined or proclined (British Standards Institute classification).

CLASS II DIVISION 2 INCISOR RELATIONSHIP

The lower incisal edges occlude posterior to the cingulum plateau of the upper incisors, and the upper central incisors are retroclined (British Standards Institute classification).

CLASS II MOLAR RELATIONSHIP

The mesiobuccal cusp of the upper molar lies anterior to the buccal groove of the lower molar.

CLASS III INCISOR RELATIONSHIP

Two or more of the lower incisal edges occlude anterior to the cingulum plateau of the upper incisors (British Standards Institute classification).

CLASS III MOLAR RELATIONSHIP

The mesiobuccal cusp of the upper molar lies posterior to the buccal groove of the lower molar.

COMPETENT LIPS

Upper and lower lips contact without muscular activity, at rest.

COMPLETE OVERBITE

The lower incisors occlude with the upper incisors or palatal mucosa.

COUPLE

A pair of equal and opposite parallel forces applied to a body.

CROSSBITE

An abnormal relationship between occluding teeth in a buccolingual and/or labiolingual direction.

CROWDING

Where there is insufficient space to accommodate the teeth in perfect alignment in an arch, or segment of an arch.

CURVE OF SPEE

A convex curve, when viewed in the sagittal plane, produced by the curvature of the cusps and incisal edges of the mandibular teeth. The depth of the curve positively correlates with the depth of the overbite.

DIAGNOSTIC (KESLING) SETUP

A diagnostic laboratory procedure where teeth are sectioned from a duplicate model and realigned manually into the proposed position to assess the aesthetic and occlusal outcome of a proposed treatment plan.

DILACERATION

The presence of an abnormal bend or curve in the root or crown of a tooth.

FIXED APPLIANCE

An appliance that is bonded onto the teeth and cannot be removed by the patient.

FRANKFORT PLANE

A line joining the upper border of the external auditory meatus to the inferior border of the orbit. Represents the natural head position and is usually parallel to the horizon.

FRENUM

A vertical band of oral mucosa that attaches the lips/cheeks to the alveolar mucosa of the maxilla or mandible.

FUNCTIONAL APPLIANCE

A removable or fixed appliance, which alters the posture of the mandible, causing stretching of the facial soft tissues, to produce a combination of dental and skeletal changes.

GENIOPLASTY

Surgical procedure undertaken to reposition the bony chin anteroposteriorly, vertically and/or transversely.

HEADGEAR

An extraoral appliance using anchorage from the occiput or cervical area to apply forces to the teeth or jaws for tooth movement or growth modification, respectively.

HYPODONTIA

When one or more permanent teeth (excluding third molars) are congenitally absent.

IDEAL OCCLUSION

Anatomically perfect arrangement of the teeth.

IMBRICATION

Overlapping of incisors due to crowding.

IMPACTION

Impeded tooth eruption, usually because of displacement of the tooth or mechanical obstruction (e.g. a supernumerary tooth).

INCOMPETENT LIPS

When active muscle contraction is required for the lips to contact each other.

INCOMPLETE OVERBITE

The lower incisors do not occlude with the opposing upper incisors or palatal mucosa when the buccal segment teeth are in occlusion.

INFORMED CONSENT

The process of providing the patient with all relevant information regarding their treatment options. This should be a continual process discussing details of treatment, alternatives, risks, benefits and consequences of not treating. For consent to be valid the patient/guardian should fully understand all the implications and treatment should not be coerced.

INFRAOCCLUSION

Positioning of a tooth below the occlusal plane.

INTERFERENCE (OCCLUSAL)

An occlusal contact occurring during mandibular closure from centric relation into centric occlusion that results in a mandibular displacement.

INTERMAXILLARY

Between opposing dental arches. For example, intermaxillary elastics connect the maxillary and mandibular dental arches to effect certain tooth movements.

INTERPROXIMAL ENAMEL REDUCTION (IPR)

The removal of small amounts of interproximal enamel in order to create space for tooth alignment.

INTRAMAXILLARY

Within the same dental arch. For example, intramaxillary elastics are used to close space from within the same arch.

LABIAL SEGMENT

The incisor teeth.

LEVELLING

Stage of orthodontic treatment aimed at flattening the curve of Spee for overbite reduction.

MALOCCLUSION

Variation from an ideal occlusion

MANDIBULAR DISPLACEMENT

When closing from the rest position the mandible displaces (either laterally or anteriorly) to avoid a premature contact.

MIDLINE DIASTEMA

A space between the central incisors. Most common in the upper arch.

MIGRATION

Physiological (minor) movement of a tooth.

MOMENT (OF A FORCE)

The tendency of a force to cause rotation.

NATURAL HEAD POSITION

A standardised reproducible head position used for dento-­?skeletal assessment.

NON-­EXTRACTION TREATMENT

Orthodontic treatment without extraction of permanent teeth, excluding the third molars.

OVERBITE

Vertical overlap of the upper and lower incisors when viewed anteriorly. May be described in millimetres, thirds or percentage overlap of the lower incisors.

OVERJET

The horizontal distance between the labial surfaces of the mandibular incisors and the incisal edge of the most prominent maxillary incisor. Normal overjet is 2-­?4mm.

POSTERIOR OPEN BITE

Occurs when the teeth are in occlusion and there is a space between the posterior teeth.

RELAPSE

The return towards the original features of a malocclusion following orthodontic treatment.

REMOVABLE APPLIANCE

An appliance that can be removed by the patient for the maintenance of oral hygiene.

RETENTION

The final phase of orthodontic treatment aimed at stabilisation of corrected tooth positions.

REVERSE OVERJET

The lower incisors lie anterior to the upper incisors. When only one or two incisors are involved the term anterior crossbite is commonly used.

ROTATION

When a tooth is twisted about its long axis.

SKELETAL PATTERN

The relationship between the maxilla and the mandible in the vertical, horizontal and transverse planes.

SMILE ARC

The relationship between the curvature of the maxillary incisal edges and canine tips to the curvature of the upper border of the lower lip when smiling.

SPACING

Where the teeth do not touch interproximally and there are gaps between adjacent teeth. Can be localised or generalised.

SUPERNUMERARY TEETH

Teeth in excess of the normal series. More common in males. Common examples in the premaxilla include conical and tuberculate supernumeraries and in the lower arch supplemental teeth.

TILTING/TIPPING

Movement of the root and crown of a tooth in opposite directions around a fulcrum.

TORQUE

Movement of the root apex bucco-­?lingually with no or minimal movement of the crown.

TRANSSEPTAL FIBRES

Periodontal fibres interconnecting adjacent teeth.

TRAUMATIC OVERBITE

Contact between the lower incisors and palatal mucosa that results in pain, inflammation, recession and/or ulceration.