Orthodontic Dictionary




AAO - American Association of Orthodontists.  The AAO is a professional association of educationally qualified orthodontic specialists dedicated to advancing the art and science of orthodontics and dentofacial orthopedics, improving the health of the public by promoting quality orthodontic care, and supporting the successful practice of orthodontics.

Abfraction - Tooth tissue loss not caused by cavities that usually occurs at the gingival margin.  

Acrylic - Methyl methacrylate, an organic resin commonly used for the construction of dental appliances, including appliances for active orthodontic tooth movement.

Activator - A removable orthodontic appliance that aids in growth guidance 

Adhesive Resin - The luting agent used with composite resins to bond (e.g. brackets) to the tooth structure.

Anchorage - In orthodontics, anchorage is a resistance to force that may come from a variety of anatomical components including teeth, bone, soft tissue, and implants.

Ankyloglossia - The attachment of the tip of the tongue to the floor of the mouth or the lingual alveolar ridge. It restricts mobility of the tongue and may lead to a speech impediment. Also called “tongue-tie”.

Ankylosis - Dental ankylosis prevents both eruption and orthodontic movement due to the fusion of a tooth to alveolar bone. In a growing child, an ankylosed tooth appears to 'submerge' as adjacent unaffected teeth and alveolar bone continue their normal pattern of eruption and growth.

Appliance - Any device designed to influence the shape and/or function of the teeth, jaws, and oral structures.

  • Fixed appliance - A bonded or banded appliance affixed to individual teeth or groups of teeth.
  • 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 (e.g., activator, bionator).
  • Orthodontic appliance - Any device used to influence the position of teeth and jaws.
  • Orthopedic appliance - Any device used to influence the growth or position of bones.
  • Removable appliance - An appliance that can be removed from the mouth and replaced at will by the patient.

Arch - Collectively, the teeth of either jaw, i.e., the term maxillary arch would include all teeth in the maxillary (upper jaw) arch.



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

Biomechanics - The study of mechanical principles applied to biological functions (in the case of orthodontics, the involved oral structures).

Biteblock - An upper or lower removable appliance, usually covering the occlusal surfaces of the teeth, used for vertical control or for TMJ problems.

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

Board Certified - The status of an orthodontist who has successfully completed both the Written and the Clinical Examination administered by The American Board of Orthodontics

Bonding - The process by which orthodontic attachments are affixed to the teeth by an adhesive.

  • Direct bonding - An intraoral procedure during which orthodontic attachments are placed on a tooth surface directly.
  • Indirect bonding - A two-step process by which orthodontic attachments are affixed temporarily to study cast teeth and then transferred to the mouth by means of a molded matrix that preserves their predetermined orientation and permits them to be bonded simultaneously.

Braces - are fixed devices used in orthodontics that align and straighten the teeth and help position them relative to an individual's bite, while also aiming to improve dental health. They are often used to correct underbites, as well as malocclusions, overbites, open bites, deep bites, cross bites, crooked teeth, and various other flaws of the teeth and jaw.

Bruxism - also known as 'tooth grinding', bruxism is the parafunctional grinding of teeth usually due to an involuntary oral habit.

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



Cephalometric radiograph - A standardized radiograph of the head characterized by a precisely defined relationship among x-ray source, subject and film.

Cephalometric tracing - A fine line tracing on an acetate film overlay of salient cephalometric structures, landmarks and pertinent measurements, which is used for diagnostic purposes.

Cervical appliance - Primarily an extraoral appliance that, when activated, delivers responsive force, by means of a pad, placed on the back of the neck.

Chin cap - A component of an extraoral orthopedic appliance capable of delivering superiorly and posteriorly directed force to the chin.

Cleft lip - A unilateral or bilateral congenital fissure in the upper lip, usually lateral to the midline.

Cleft palate - A unilateral or bilateral congenital fissure in the palate.

Clicking - A term applied to abnormal soft tissue sounds (usually audible or by stethoscope or on palpation) emanating from one or both temporomandibular joints during jaw movement.

Closed bite - Excessive vertical overlap of the anterior teeth; deep bite.

Comprehensive orthodontics - A coordinated diagnosis and treatment leading to the improvement of a patient's craniofacial dysfunction and/or dentofacial deformity which may include anatomical, functional and/or esthetic relationships.

Computerized cephalometrics - The process of entering cephalometric data in digital format for analysis by any one or more of a variety of analyses available in software format.

Computerized digital imaging - Substitution of a radiation detector plate for radiographic film in the film cassette. The detectors store the radiation energy at each pixel as a latent image for release into the 13 computer in digital format. Advantages include a radiograph with a much wider dynamic range for improved edge enhancement, and the ability to change contrast in specific regions.

Cosmetic orthodontics - Orthodontic therapy, the purpose of which is limited to improving the appearance of the teeth or face.

Crossbite - An abnormal relationship of a tooth or teeth to the opposing teeth, in which normal buccolingual or labiolingual relationships are reversed. Also called Reverse articulation.

Crowding - Dental malalignment caused by inadequate space for the teeth.

Curve of Spee - The anatomic curve established by the occlusal and incisal surfaces of the tooth crowns, as projected into the median plane in either dental arch. This curve is generally concave upward in the mandibular arch and convex for the maxillary arch.

Curve of Wilson - Because the long axes of the mandibular molars and premolars converge towards the midline, the occlusal surfaces of these teeth, bilaterally, form a curve in a buccolingual direction.



Debanding - The removal of cemented orthodontic bands.

Debonding - The removal of bonded orthodontic attachments.

Decompensation - Orthodontic tooth movement that is done to bring teeth into optimum position in their respective jaws in preparation for orthognathic surgery.

DDS or DMD Doctor of Dental Surgery or Doctor of Dental Medicine - two equivalent degrees awarded by dental schools to graduates of the doctoral dental program.

Deep bite - Excessive overbite; closed bite.

Dehiscence - A fissural defect in the facial alveolar plate extending from the free margin apically.

Dental plaque - A “conglomeration” of bacteria and organic matter which adheres to the teeth and related structures.

Dentin - The hard tissue of the tooth surrounding the central core of nerves and blood vessels (pulp). It forms the bulk of a tooth and is covered by enamel on the coronal part and cementum on the radicular portion of the tooth.


  • Primary dentition - Teeth that develop and erupt first in order of time and are normally shed and replaced by permanent (succedaneous) teeth.
  • Transitional dentition - A phase in the change from primary to permanent dentition, in which the primary molars and canines are in the process of exfoliating and the permanent successors are emerging.
  • Adolescent dentition - The dentition that is present after the normal loss of primary teeth and prior to cessation of growth that could affect orthodontic treatment.
  • Adult dentition - The dentition that is present after the cessation of growth that could affect orthodontic treatment.

Dentofacial deformity - Malformation of the dental and/or facial structures characterized by disharmonies of size, form and function, malocclusion, cleft lip and palate and other skeletal or soft-tissue deformities, including various types of muscular dysfunction.

Diagnostic set up - A laboratory procedure in which teeth are removed from the plaster cast and repositioned in wax. It may be used as a diagnostic tool to evaluate alternative treatment plans, particularly in interdisciplinary treatment, when a tooth size discrepancy exists or when orthognathic surgery is required along with orthodontic treatment.

Diastema - A space between two adjacent teeth in the same dental arch.

Direct reimbursement - A self-funded program in which the individual is reimbursed, based on a percentage of the cost of dental care. Allows beneficiaries to seek treatment from the dentist of their choice.

Discrepancy - A disparity in the ratio of tooth size to arch length.

Dolichocephalic - Long, narrow cranial form; the opposite of brachycephalic.

Dolichofacial - A facial pattern characterized by a long, narrow face; preferred term is leptoprosopic.



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

Edge-to-Edge occlusion - An occlusion in which the anterior or posterior teeth of both jaws meet along their incisal or buccal cuspal edges. Often associated with a Class III molar relationship.

Edgewise appliance - A fixed orthodontic appliance characterized by attachment brackets that have a rectangular slot for engagement of a rectangular orthodontic wire.

Elastics (rubber bands) - Variously used as Class II elastics, Class III elastics, Diagonal elastics, Updown (vertical) elastics and cross-elastics. Usually made of latex.

Elastomeric ligature - A polymeric or rubber band or thread that is stretched around the tie-wings of an orthodontic bracket for the purpose of preventing disengagement of an archwire or auxiliary from the bracket-slot.

Embrasure - it is the space that is formed around the adjoining contact of two teeth.

Enamel - The hard, thin, translucent layer of calcified tissue that surrounds the dentin in the coronal part of the tooth. It is also the hardest material in the human body.

Enameloplasty - the reshaping of the enamel, often done as occlusal adjustment.

Eruption - Movement of teeth in an incisal or occlusal direction into the oral cavity through the supporting bone and gingival tissue.

Expansion - Enlargement; often used to describe the mechanical widening of the dental arches.

Expansion screw - A mechanical device incorporated in a removable or a fixed appliance that is used to enlarge the dental arch in some dimension.

Extraction - Removal of a tooth.

Extrusion - A translational form of tooth displacement with movement occlusally directed and parallel to the long axis of the tooth.



Facial asymmetry - A term used in the negative sense to describe a reduction of similarity or proportion between the right and left sides of the face or the craniofacial skeleton. May also be applied to any structure that is too large or small so as to be out of balance or not proportional to other structures.

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.

Facial convexity - A term similar to facial concavity, but describes an outwardly rounded curve from the forehead to the lips to the chin. Facial convexity indicates a fullness in the lip region and is associated with a Class II malocclusion.

Facial esthetics - A term pertaining to facial beauty, symmetry, balance and proportion.

Facial form - The configuration, shape or appearance of the face from an anterior frontal view.

Facial growth - The process of enlargement of the craniofacial skeleton and soft tissues.

Facial proportions - An assessment of the balance of the face from a frontal or profile view. The intent of the assessment is to determine asymmetry or imbalance.

Facial type - A classification of the face. Three facial types are described: brachycephalic or euryprosopic (wide, short), dolichocephalic or leptoprosopic (long, narrow), and mesocephalic or mesoprosopic (average).

Finishing - A stage of treatment that is toward the end of comprehensive orthodontic care in which the teeth are placed in their final positions.

Fixed appliance - An orthodontic appliance whose attachments are bonded or cemented to the teeth and cannot be removed by the patient. Generally termed 'braces' by the lay public.

Free-way space - The clearance or interocclusal distance between the maxillary and mandibular teeth when the mandible is in its postural resting position.

Frenectomy - The surgical removal or repositioning of a frenum. Performed to enhance the stability of a corrected diastema or to alleviate a “tongue-tie”.

Frenum - A fold of mucous membrane and underlying fibrous tissue that connect lip, cheek or tongue to the alveolar mucosa. (May be labial or lingual).

Functional occlusion - An arrangement of the teeth intended to minimize stress on the temporomandibular joint; maximize function, stability and esthetics of the teeth; and provide for protection and health of the periodontium.




Genioplasty - A surgical procedure designed to reshape the contour of the chin, usually by augmentation or reduction.

Gingiva - The fibrous investing tissue, covered with epithelium, which immediately surrounds the teeth and is contiguous with the periodontal ligament and with the mucosal tissues of the mouth.

Gingival attachment - The fibrous attachment of the gingiva to the tooth/teeth.

Gingivitis - Inflammation of the gingiva.

Group function - Multiple simultaneous contacts of several maxillary and mandibular teeth on the working side in lateral movements of the jaw during which forces are distributed on a number of teeth.

Growth forecast (or prediction) - A predicted estimation of change in the location or size of the bones of the craniofacial skeleton due to expected growth and development and/or the effects of treatment.

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

Gummy smile - A popular term for excessive exposure of maxillary gingival tissue during a full smile.



Hawley appliance - A Hawley retainer modified to allow for minor corrective procedures.

Hawley retainer - A passive removable acrylic and wire appliance, generally used to stabilize teeth in their new position after orthodontic correction. 

Headcap - The component of an (primarily) extraoral appliance that distributes and transfers responsive force to the cranium.

Headgear - Common generic term for an extraoral traction appliance that can be used for growth modification, tooth movement and anchorage.

Herbst appliance - Fixed or removable appliance designed to effect an orthopedic change of the mandible much like an activator.

Hypodontia - Congenital absence of one or more teeth.

Hypoplasia - Incomplete development of a tissue or structure.




Imaging - The process of acquiring representations of structures in either two or three dimensions.

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

Impression - An impression in orthodontics is typically produced by placing an elastic compound like alginate in a preformed tray, and placing the loaded tray over the teeth until the material stiffens. The impression is removed from the mouth and may be filled with plaster to produce an exact positive reproduction of the teeth or dental arch.

Infection control - Measures practiced by healthcare personnel in healthcare facilities to decrease transmission and acquisition of infectious agents (e.g., proper hand hygiene, scrupulous work practices, use of personal protective equipment (PPE) [masks or respirators, gloves, gowns, and eye protection]. These guidelines are set by CDC, OSHA, etc.

Interceptive orthodontics - An extension of preventive orthodontics that may include localized tooth movement.

Interdental spacing - Spacing between the teeth.



Jaw - A common term for either the maxilla (upper jaw) or mandible (lower jaw).

Jaw relationship - The position of the upper jaw in relationship to the lower jaw; usually an anteroposterior or transverse assessment.



Leeway space - The difference between the combined widths of the three buccal primary teeth (canine and two molars) and their permanent successors (canine and two premolars).

Le Fort surgical procedure - Surgical procedure in which parts of the upper face are completely separated from their supporting structures and repositioned to effect corrective alignment.

  • Le Fort I surgical procedure - A horizontal segmented fracture of the alveolar process of the maxilla, in which the teeth are usually contained in the detached portion. 
  • Le Fort II surgical procedure - A pyramidal fracture of the midfacial skeleton with the principal fracture lines meeting at an apex at or near the superior aspect of the nasal bones. The lateral orbital rims and nasal processes are typically intact.
  • Le Fort III surgical procedure - A craniofacial dysjunction fracture in which the entire maxilla and one or more facial bones are completely separated from the cranial base. Also called Transverse facial fracture.

Leveling - A phase of comprehensive orthodontic treatment when fixed appliances are used to change the line of intercuspation from a curve to a straight line; to align the teeth in the same plane.

Ligation - The act of tying, of applying a ligature. In orthodontics the term is often used to denote tying a wire to the orthodontic brackets.

Ligature - A tie that secures the archwire in the bracket-slot typically annealed wire, rubber, or a polymer.

Light-wire technique - An orthodontic treatment modality in which the appliance components to be activated are relatively flexible. Small force values, active over long time periods are used.

Limited orthodontic treatment - Typically focuses on limited objectives, not necessarily involving the entire dentition. It may be directed at the only existing problem, or at only one aspect of a larger problem in which a decision is made to defer or forego a more comprehensive plan of therapy.

Lingual - Of or pertaining to the tongue. A term used to describe surfaces and directions toward the tongue. lingual appliances Orthodontic appliances fixed to the lingual (toward the tongue) surface of the teeth.

Lingual arch - A single orthodontic wire, that traverses the lingual surfaces of the teeth, usually from molar to molar. Generally used for stabilization, as a holding arch for space maintenance, for expansion, or to provide anchorage for intermaxillary traction.

Lip bumper - An appliance designed to eliminate excessive lip pressure on the anterior teeth and transfer that force to the molars. Typically consists of a labial archwire with or without an anterior plastic pad, fitted into tubes on the molars. 

Lip incompetence - A gap between the relaxed upper and lower lips because of a vertical hard and soft tissue imbalance.

Long-face syndrome - A craniofacial pattern characterized by a long and narrow face, an increased mandibular plane angle, an anterior open bite malocclusion and lip incompetence. It is thought by some to result partly from a lack of adequate airway.



Macrodontia - Teeth that are larger than normal.

Malocclusion (relationship of teeth in occlusion) - A deviation in intramaxillary and/or intermaxillary relations of teeth from normal occlusion. Often associated with other dentofacial deformities. See Angle classification.

Mandible - The lower jaw.

Mandibular osteotomy - Surgical sectioning of the mandible into two or more parts to allow repositioning of the resulting components.

Maxilla - Paired facial bones that form the base for the upper dental arch, floor of the nose and much of the lower border of the orbit and cheek bones.

Maxillary osteotomy - Surgical sectioning and repositioning of maxillary bone structure to alter bone and jaw relationships

Microdontia - Abnormal smallness of teeth.

Micrognathia - An abnormally small jaw.




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

Occlusal plane - The imaginary surface on which upper and lower teeth meet in occlusion. It is actually a compound curved surface, but is commonly approximated by a plane (straight line from the side view) based on specific reference points within the dental arches.

Open bite - Lack of tooth contact in an occluding position.

Orthognathic surgery - Surgery to alter relationships of teeth and/or supporting bones, usually accomplished in conjunction with orthodontic therapy.

Orthopedic - Correction of abnormal form or relationship of bone structures. May be accomplished surgically (orthognathic surgery) or by the application of appliances to stimulate changes in the bone structure by natural physiologic response (orthopedic therapy).

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

Overjet -  Horizontal projection of upper teeth beyond the lower front teeth, usually measured parallel to the occlusal plane. 



Palate - The bone and soft tissue that forms the roof of the mouth and is connected to the nasal septum and floor of the nose in the midline.

Palatal expansion - The lateral movement of the maxillae to increase palatal width.

Panoramic radiograph - A radiograph of the jaws, taken with a specialized machine designed to present a panoramic view of the full circumferential length of the jaws on a single film.

Periodontal membrane (or ligament)  -The fibrous tissue around teeth that occupies the space between tooth root and alveolar bone.  It provides a physical attachment of the tooth to the bone and nourishment to the surface of the root and the cells that permit tooth movement.



Radiograph - A permanent image, typically on film, produced by ionizing radiation. Sometimes called an xray after the most common source of image-producing radiation.

Resorption - Physiologic or pathologic removal of hard tissue (bone or root).

Retainer - Any orthodontic appliance, fixed or removable, that is used to maintain the position of the teeth following corrective treatment.

Root resorption - Resorption of a part of the root of a tooth. May be either internal (pulpal) or external.



Self ligation - Specifically used with brackets that have within them the ligation mechanism to hold the wire.

Separator - An object/ agent (elastic module, brass wire, spring) used for separating teeth.

Serial extraction - A program of selective or guided extraction of primary and sometimes permanent teeth over a period of time, with the objective of relieving crowding and facilitating the eruption of remaining teeth into improved positions.

Space maintainer - A prosthetic replacement for prematurely lost primary teeth intended to prevent closure of the space before eruption of the permanent successors.

Supracrestal fiberotomy - The procedure of severing the insertion of the supracrestal group of gum fibers from the tooth; used as an aid to retain the correction of rotation.



Temporary anchorage device (TAD) - A device that is temporarily fixed to bone for the purpose of enhancing orthodontic anchorage either by supporting the teeth of the reactive unit or by obviating the need for the reactive unit altogether, and which is subsequently removed after use.

TMD - Temporomandibular dysfunction.

TMJ (temporomandibular joint) - One of the two paired articulations between the temporal bones of the skull and the mandible. 

Therapeutic diagnosis - An assessment of the objectives and available methods of treatment in light of conditions existing in the individual patient.

Thumb (or finger) sucking - A normal infantile activity that sometimes extends into middle or late childhood. In certain situations, it may produce or exacerbate malocclusion.

Tongue crib - An appliance used to control undesirable and potentially deforming tongue movements, i.e., a posturing or thrusting of the tongue between the front teeth.

Tongue thrust - Th positioning of the tongue between the front teeth, especially in the initial stage of swallowing. This action, often combined with a resting position of the tongue between the teeth, can inhibit normal eruption and produce an open bite.

Tooth size discrepancy - Lack of proportional harmony in the width of various tooth crowns and the available space in the dental arch, causing relative spacing or crowding in different parts of the dentition.



Underbite-  An non-technical term for negative overjet, or when the lower front teeth are positioned in front of the upper front teeth when biting.