An Introduction to Orthodontics, 2nd Edition

Definitions

ANCHORAGE

The source of resistance to the forces generated in reaction to the active components of an appliance.

ANTERIOR OPEN BITE

There is a space vertically between the incisors when the buccal segment teeth are in occlusion.

BALANCING EXTRACTION

Extraction of the same (or adjacent) tooth on the opposite side of the arch to preserve symmetry.

BIMAXILLARY PROCLINATION

Both upper and lower incisors are proclined relative to their skeletal bases.

BODILY MOVEMENT

Equal movement of the root apex and crown of a tooth in the same direction.

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.

CINGULUM PLATEAU

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

COMPENSATING EXTRACTION

Extraction of the same tooth in the opposing arch.

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.

CROWDING

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

DENTO-ALVEOLAR COMPENSATION

The inclination of the teeth compensates for the underlying skeletal pattern, so that the occlusal relationship between the arches is less marked.

HYPODONTIA

This term is used when one or more permanent teeth (excluding third molars) are congenitally absent. The equivalent American nomenclature is oligodontia.

IDEAL OCCLUSION

Anatomically perfect arrangement of the teeth. Rare.

IMPACTION

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

INCOMPETENT LIPS

Some muscular activity is required for the lips to meet together.

INCOMPLETE OVERBITE

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

LEEWAY SPACE

The difference in diameter between the deciduous canine, first molar, and second molar, and their permanent successors (canine, first premolar, and second premolar).

LINGUAL CROSSBITE

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

MALOCCLUSION

Variation from ideal occlusion which has dental health and/or psychosocial implications for the individual. NB The borderline between normal occlusion and malocclusion is contentious (see Chapter 1).

MANDIBULAR DEVIATION

The path of closure of the mandible starts from a postured position.

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.

NORMAL OCCLUSION

Acceptable variation from ideal occlusion.

OVERBITE

Vertical overlap of the upper and lower incisors when viewed anteriorly: one-third to one-half coverage of the lower incisors is normal; where the overbite is greater than one-half it is described as being increased; where the overbite is less than one-third it is described as being reduced.

OVERJET

Distance between the upper and lower incisors in the horizontal plane. Normal is 2–4 mm.

RELAPSE

The return, following correction, of the features of the original malocclusion.

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

A tooth is twisted around its long axis.

SPACING

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

TILTING MOVEMENT

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

TORQUE

Movement of the root apex buccolingually, either with no or minimal movement of the crown in the same direction.

TRAUMATIC OVERBITE

The occlusion of the lower incisors with the palatal mucosa has led to ulceration.

UPRIGHTING

Mesial or distal movement of the root apex so that the root and crown of the tooth are at an ideal angulation.



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