Acrylic - Methyl methacrylate, an organic resin commonly used for the construction of dental appliances, including orthodontic treatment and retention appliances

Activation - The process of deforming an appliance part from its passive state (e.g., the stretching of an elastic) and completing its engagement to produce a force system transmitted by the appliance to the dentition.

Activator - A removable growth guidance orthodontic appliance, originally developed by Pierre Robin, Viggo Andresen and Karl Haupl, with later modifications by Schwarz, Bimler, Balters, Franker, Fleischer, Peters, etc. Also called a functional appliance.

Adams Clasp - A circumferential retention clasp (see crib) designed by C. Philip Adams to stabilize removable

Alveolar Bone - The bone that surrounds and supports the roots of the teeth.

Fixed Appliance - A bonded or banded appliance affixed to individual teeth or groups of teeth.

Orthodontic Appliance - Any device used to influence growth or the position of teeth and jaws

Removable Appliance - An appliance not attached to teeth and removable from the mouth.

Orthopedic Appliance - Any device used to influence the growth or position of bones.

Functional Appliance - Any device, removable or fixed, designed primarily to effect skeletal and/or dental changes by modifying and utilizing the neuromuscular forces of the stomatognathic system (i.e., activator, bionator).

Band (orthodontic) - A thin metal ring, usually stainless steel, which serves to secure orthodontic attachments to a tooth. The band, with orthodontic attachments welded or soldered to it, is closely adapted to fit the contours of the tooth and then cemented into place.

Biteplate or Bite plane - A removable orthodontic appliance designed to open the bite and/or prevent selected teeth from occluding.

Bracket An orthodontic attachment that is secured to a tooth (either by bonding or banding) for the purpose of engaging an arch wire. Brackets can be fabricated from metal, ceramic or plastic.

Chin Cap - A component of an extraoral orthopedic appliance capable of delivering superiorly and posteriorly directed force to the chin. Cosmetic Orthodontics - Orthodontic therapy whose purpose is limited to improving the appearance of the teeth or face.

Crib - A type of wrought-wire clasp that surrounds or encloses a tooth; occasionally, used to describe a fixed transpalatal tongue and/or finger interceptive appliance.

Debanding - The removal of cemented orthodontic bands.

Deep Bite - Excessive overbite; closed bite.

Dental Plaque - An adherent conglomeration of bacteria and organic matter on the teeth and related structures that is often the first stage in caries or periodontal disease.

Early Orthodontic Treatment - Orthodontic treatment started while patient is still in transitional or primary dentition.

Edgewise Appliance - A fixed orthodontic appliance characterized by attachment brackets with a rectangular slot for engagement of an orthodontic wire. The most common appliance in use today.

Ectopic - Located away from normal position; often used to describe a condition in which a tooth develops or erupts in an abnormal position.

Facial Concavity - A term applied to the analysis of a profile. The shape is described as an inwardly rounded curve from the forehead to the lips to the chin. A concave facial profile is often associated with a Class III malocclusion.

Facebow - In conjunction with extraoral traction anchored on the back of the head or neck, a long metal bow which inserts intraorally into an orthodontic appliance. Generally used to move teeth or bones posteriorly or prevent their forward movement.

Full Treatment - Comprehensive orthodontic treatment including both upper and lower dental arches.

Genial - Pertaining to the chin.

Gemination - Abnormal tooth development due to incomplete division of a single tooth bud.

Gingiva - The tissue that surrounds the teeth, consisting of a fibrous tissue that is continuous with the periodontal ligament and mucosal covering.

Gingivitis - Inflammation of the gingiva.

Graft - A portion of tissue used for implantation.

Grinding - Usually a term synonymous with bruxism or parafunctional activity.

Guidance, Developmental - A planned orthodontic and orthopedic effort to influence the growth of the jaws and eruption of the teeth, with the objective of guiding abnormal development into a normal situation. This generally requires a combination of carefully timed appliance therapies and supervisory examinations involving radiographic and other diagnostic records at various stages of development. This may be required from the earliest date of detection of a developing malformation until the craniofacial skeleton is mature.

Guide Plane - A fixed or removable orthodontic appliance designed to deflect the functional path of the mandible and alter positions of specific teeth.

Jumping the Bite - The correction of a crossbite brought about by horizontal movements of teeth and, occasionally, the jaw, to their correct position.

Headgear - Common generic term for extraoral traction for growth modification, tooth movement and anchorage.

Hooks - Attachments soldered or welded to arch wires for the placement of elastics, headgear, or elastic chains.

Impaction (tooth) - A condition describing the total or partial lack of eruption of a tooth well after the normal age for eruption.

Implant - Generally an artificial structure placed into bone, which provides for prosthetic replacement of some missing structure. Also used to describe a graft placed in soft tissue.

Impression - A negative image of a tooth or dental arch. An impression is produced by placing an elastic compound like alginate in a preformed tray and inserting the tray into the mouth around the teeth until the compound stiffens. The impression is removed from the mouth and filled with plaster to produce an exact positive reproduction of the teeth or dental arch.

Intrusion - A translational form of tooth movement directed apically and parallel to the long axis.

J-hook Headgear - A (primarily) extraoral appliance defined by a pair of metallic components, each in the shape of the letter 'j', that deliver force bilaterally to anterior, intraoral sites.

Jumping the Bite - The correction of a crossbite brought about by horizontal movements of teeth and, occasionally, the jaw, to their correct position.

Labial - Of or pertaining to the lip. Identifies a surface facing the lips. The same as 'facial' in the anterior portion of the dentofacial complex.

Leveling Wire - Orthodontic wire, ordinarily round (in cross-section) and exhibiting low flexural stiffness, used in the leveling phase of treatment.

Lingual - Of or pertaining to the tongue. A term used to describe surfaces and directions toward the tongue.

Luxation - Forceful movement or displacement of an anatomic structure. In dentistry, may describe displacement of the mandibular condyle or the intentional movement of a tooth in its alveolus with tearing of the periodontal fibers; sometimes used in an effort to free an ankylosed tooth.

Macrodontia - Teeth that are larger than normal.

Nightguard - A removable plastic appliance worn at night to prevent deleterious effects of nocturnal parafunctional activity (i.e., clenching, bruxism). See mouthguard.

Occlusal - Pertaining to the chewing surfaces of the posterior teeth. May be used to identify those tooth surfaces, as well as the direction (upward in the lower arch, downward in the upper).

Occlusion - The relationship of the maxillary and mandibular teeth as they are brought into functional contact.

Ortho- A prefix denoting straight or correct.

Orthodontist - A dental specialist who has completed an advanced post-doctoral course, accredited by the American Dental Association of at least two academic years in the special area of orthodontics.

Overbite - Vertical overlapping of upper teeth over lower teeth, usually measured perpendicular to the occlusal plane.

Palate - The bone and soft tissue closing the space encompassed by the upper alveolar arch, with a posterior extension to the pharynx. Forms the roof of the mouth and is connected to the nasal septum and floor of the nose in the midline.

Periapical - Pertaining to the area and tissues around the apex (tip) of the root of a tooth

Periodontics - That dental specially concerned with the maintenance of the health and integrity of the periodontal tissues that support the teeth.

Protraction - Anterior displacement of the teeth and/or bones of the face.

Protrusion - The state of being anteriorly positioned.

Radiographic Imaging - The process of acquiring representations of structures using ionizing radiation.

Replantation - The replacement of a tooth that has been avulsed, usually as the result of an accident.

Rest Position - The normal resting position of the mandible, with teeth apart and muscles relaxed.

Root - That part of the tooth not covered by enamel, normally lying within the alveolus where it is attached to the bone by the periodontal membrane (ligament).

Separation - An orthodontic procedure for slightly separating teeth to facilitate placing bands.

Stomion - Intersection of the closed upper and lower lips.

Supraocclusion - Overeruption of a tooth or teeth beyond the normal level, often as a result of tooth-loss or irregularity in the opposing arch.

Syndrome A group of symptoms and/or deformities that occur together in a recognizable pattern, defining a specific disease or condition.

Telescoping Bite - Total lingual crossbite of the lower arch.

Torque - A third order couple moving the crown in one direction and the root in the opposite direction.

Underbite - An ambiguous non-technical term for negative overjet. (archaic)

Universal Appliance - An orthodontic appliance developed by S.R. Atkinson, combining some of the principles of edgewise and ribbon arch appliances with very light arch wires.

Vertex (anatomy) - The most superior point on the top of the skull.

W Arch - W-shaped maxillary expansion arch, usually soldered to the lingual of the maxillary molars. (Also known as Porter arch.)

X-Ray - Electromagnetic radiation produced when electrons strike a target under high voltage in a vacuum. The term is sometimes used incorrectly as a synonym for radiograph.

Zygoma - The bone that articulates with the maxilla to form the lateral wall of the orbit and the cheek bone itself. Its posterior extension, the processus temporalis, articulates with the zygomatic process of the temporal bone, and together they provide major support for the muscles of mastication.