A a see Point a (subspinale). Aao

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AAO Glossary 2012

©2012, American Association of Orthodontists

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A See Point A (subspinale).

AAO See American Association of Orthodontists.

AAOF See American Association of Orthodontists Foundation.

AAOIC See American Association of Orthodontists Insurance Company.

AAOSI See American Association of Orthodontists Services, Inc.

ABO See American Board of Orthodontics.

abfraction The pathologic loss of hard tooth substance caused by biomechanical loading forces. Such loss is thought to be due to flexure and chemical fatigue degredation of enamel or dentin at a site distant from the site of actual point of loading.

abrasive 1. a substance used for abrading, smoothing or polishing. 2. tending to abrade, causing irritation.

abrasive strips Thin flexible tapes or strips that are coated with abrasive particles of different grain size and are used to remove, polish and finish tooth contours. These are usually used for interproximal reduction. They can be polyester, stainless steel or diamond abrasive strips.

acromegaly (from Greek akros “extreme” or “extremities” and megalos “large”) A disease caused by increased activity of the anterior pituitary producing excess growth hormone (hGH) after epiphyseal plate closure and characterized in part by a marked lengthening of the mandible.

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

activation The process of deforming an appliance or a part of an appliance 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.

activation site The intraoral location of the activating process, often where the orthodontic force system is to be transmitted to the dentition.

activator 1. A removable growth guidance orthodontic appliance, originally developed by Pierre Robin, Viggo Andresen and Karl Haupl, with later modifications by Schwarz, Bimler, Balters, Frankel, Fleischer, Peters, etc. It is a type of functional appliance. 2. a chemical agent which triggers an initiator chemical to begin a chemical reaction.

Adams clasp A circumferential retention clasp (see crib) designed by C. Philip Adams to stabilize removable appliances by means of point contact with the mesio- and disto-buccal undercuts of individual buccal teeth.

adenoid face See long-face syndrome.

adenoidectomy The surgical removal of the adenoids. They may be removed for several reasons which include impaired nasal breathing and chronic infections or earaches.

adenoids Lymphatic tissue that forms a prominence of the wall of the pharyngeal recess of the nasopharynx.

adhesive resin Any resin material with incorporated adhesive chemicals such as organophosphates, HEMA (hydroxyethyl methacrylate), or 4-META (4-methacrylethyl trimelletic anhydride); in orthodontics and dentistry, it describes the luting agent used with composite resins to bond (e.g. brackets) to the tooth structure.

adolescent dentition See dentition.

adult dentition See dentition.

agenesis A failure of development. For example tooth agenesis (lack of tooth development), condylar agenesis (lack of condylar development).

agnathia A developmental anomaly characterized by the lack of development of the mandible.

air abrasion The process of altering the surface of a material by the use of abrasive particles which are propelled by compressed air.

alloy A mixture of two or more metals or metalloids that are mutually soluble in molten state. It can be binary, ternary, quaternary etc. depending upon the number of metals in it. Alloying elements are added to alter the physical properties of a pure metal. Alloys can also be classified based on their behavior such as- noble metal, base metal etc.

alveolar bone The bone that surrounds and supports the roots of the teeth.

alveolar process The unshaped ridge of maxillary or mandibular alveolar bone that surrounds and supports the roots of the teeth.

amalgam Dental amalgam is an alloy of mercury, silver, copper, tin, zinc that is used for restorative procedures.

American Association of Orthodontists (AAO) 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.

American Association of Orthodontists Foundation (AAOF) The AAOF, a 501(c)(3) organization, is the charitable arm of the AAO. The AAOF raises money for an endowment the earnings from which are used to support orthodontic research and teaching fellowships.

American Association of Orthodontists Insurance Company (a Risk Retention Group) (AAOIC) The AAOIC provides professional liability insurance for eligible United States members of the AAO. AAOIC is unique in that coverage is only available to AAO members and only orthodontists are insured by the company. The policyholders are also the shareholders of the Company. AAOIC is governed by a group of dedicated orthodontists and other experts who have one goal in mind: to provide a stable, efficiently run professional liability insurance company designed specifically to meet the unique needs of the AAO member orthodontists. See Risk Retention Group.

American Association of Orthodontists Services, Inc. (AAOSI) The AAOSI is the for-profit subsidiary of the AAO, dedicated to the evaluation and management of services that benefit the members’ pursuit of professional success and financial security through quality insurance products and other services.

American Board of Orthodontics (ABO) The ABO is recognized by the American Dental Association as the official certifying body for the specialty of orthodontics. Though sponsored by the American Association of Orthodontists, it is a separate and autonomous entity. The mission of the ABO is to establish and maintain the highest standards of clinical excellence in orthodontics.

anchorage Resistance to force. Anchorage may come from any of the following sources: intraoral – teeth, bone, soft tissue, implants; extraoral – cervical = back of the neck, occipital = back of the head, cranial = top of the head.

Andresen appliance See activator.

Angle classification of malocclusion A classification of malocclusion introduced by Edward H. Angle (1855-1930). The governing criterion is the anteroposterior relationship of maxillary and mandibular first molars.

Class I malocclusion (neutroclusion) A malocclusion in which the mesiobuccal cusp of the maxillary first molar occludes in the buccal groove of the mandibular first molar. "Class I" is sometimes incorrectly used as a synonym for normal occlusion, whereas it signifies only a normal sagittal relationship of maxillary and mandibular posterior teeth as they meet.

Class II malocclusion (distoclusion) A distal (posterior) placement of the mandibular (lower) molar, a mesial (anterior) relationship of the maxillary (upper), or a combination of the two. The mesiobuccal cusp of the maxillary first molar occludes mesial to the buccal groove of the mandibular first molar, usually near the embrasure between the mandibular molar and second premolar.

Class II, Division 1 A Class II molar relationship with proclined maxillary incisors.

Class II, Division 2 A Class II molar relationship, usually with the maxillary central incisors tipped lingually, the maxillary lateral incisors tipped labially. This malocclusion, in many instances, has and an excessive overbite.

Subdivision of any malocclusion category denotes a unilateral malocclusion classification (e.g. Class II, division 2, subdivision).

Class III malocclusion (mesioclusion) Mesial (anterior) relationship of the mandibular first molar to the maxillary first molar, a retruded relationship of the maxillary first molar to the mandibular, or a combination of the two. The mesiobuccal cusp of the maxillary first molar will typically occlude near the embrasure between the mandibular first and second molars.

angular cheilitis Inflammation of the corners of the mouth which causes redness and fissures; also called perleche.

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 Abnormal immobility, union or fusion. May occur between two bones at their articulation (i.e., TMJ) or between teeth and alveolar bone. In the latter case, the periodontal ligament is obliterated by a 'bony bridge' and the tooth root is fused to the alveolar bone. Dental ankylosis prevents both eruption and orthodontic movement. 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.

anneal To heat a material in order to remove internal stresses and create a desired degree of toughness, temper or softness to a material.

anodontia a rare disorder characterized by congenital absence of all teeth (both deciduous and permanent).

anterior deprogramming device Various types of devices or materials used to eliminate the proprioceptive influence on occlusion and mandibular closure.

antegonial notch A concavity usually present in the lower border of the mandible, immediately anterior to the angle of the mandible. A deeper than normal antegonial notch may be indicative of mandibular underdevelopment.

anterior cranial base The anterior aspect of the floor of the cranial vault, commonly delimited cephalometrically by sella turcica and nasion.

anterior guidance 1. The influence of the contacting surfaces of maxillary and mandibular incisors that guides the mandible downward and creates disarticulation of the posterior teeth. 2. The influence of the contacting surfaces of the guide pin and anterior guide table on articulator movements.

anterior nasal spine Pointed bony process at the inferior margin of the piriform aperture, formed by the forward prolongation of the two maxillae. In cephalometric radiography, the tip is often used to define the anterior end of the palatal plane.

anteroposterior The global direction perpendicular to the coronal plane of the dentofacial complex; the anterior direction/sense is forward, and the posterior direction/sense is rearward.

anthropometry Measurement of the human body and its parts.

antiflux Materials that prevent the flow of solder.

apertognathia Condition in which either the anterior or posterior teeth of opposing arch do not contact. See also open bite.

apical Of or pertaining to the apex (usually of the tooth).

apical base Maxillary and mandibular bone that support and are continuous with the alveolar processes (see basal bone). Although the demarcation between alveolar and basal bone is not specific, it is generally considered to lie at the level of the apices of the roots.

apnea A cessation, or near cessation, of respiratory airflow that lasts 10-15 seconds or longer. Also see sleep apnea.

appliance Any device designed to influence the shape and/or function of the stomatognathic system.

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 arch.

alveolar arch The U-shaped alveolar bone that surrounds the dentition of either jaw.

dental arch The composite structure of the dentition and alveolar ridge basal arch.

arch bars A rigid bar used for intermaxillary fixation in treatment of fractures of the maxilla and/ or mandible; or stabilization of injured teeth. These are generally attached to the remaining dentition or occlusal splints.

arch form The geometric shape of the dental arch or of an archwire when viewed in the horizontal plane (square, tapering, ovoid, etc.).

arch length A measurement of available space needed to align the teeth.

arch length deficiency Difference between available and required space to align the teeth (see discrepancy).

archwire A wire capable of causing or guiding tooth movement that is placed into orthodontic attachments which are affixed to the crowns of two or more teeth.

continuous archwire A wire that engages or could engage, through crown attachments, all of the erupted teeth in the maxillary or mandibular dental arch.

sectional or segmental archwire An archwire that engages, through crown attachments, only a few teeth (e.g., only the four incisors or only a posterior dental segment).

arthralgia Pain in a joint(s).

arthritis Inflammation of a joint(s).

articular Of or relating to a joint.

articulare A constructed point on lateral cephalometric films representing the intersection of three radiographic images: the inferior surface of the cranial base and the posterior outlines of the ascending rami or dorsal contour of the mandibular condyle bilaterally (A. Bjork).

articulating paper Ink coated paper strips which are used to identify occlusal contacts.

articulator A mechanical instrument that represents the temporomandibular joint and the jaws. The maxillary and mandibular casts are attached to it.

asperities Microscopic projections on metal surfaces that result from normal surface-finishing processes. Interference between opposing asperities in sliding or rolling applications is a source of friction, and can lead to metal welding and scoring.

austenitic The name given to the face-centered cubic crystal structure (FCC) of ferrous metals.

autoclave A device that is used for sterilizing equipment and instruments with saturated stream filters with constant high temperature and pressure.

axis of rotation The line in a body (or in an extension of the body) about which the body has or appears to have rotated in a nontranslational displacement.

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B See Point B.

balancing side A term used in the study of occlusion (i.e., for the non-functional side when the mandible is shifted laterally).

band (orthodontic) 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.

banding An orthodontic procedure during which bands are inserted and cemented onto teeth.

basal bone The bone that underlies, supports, and is continuous with the alveolar process (see apical base).

basal dysplasia A skeletal malrelationship related to a defect in size, shape, or position of basal bone.

basion The anterior margin of the foramen magnum, often used as a landmark on the lateral cephalogram.

Begg appliance A fixed appliance developed by P. R. Begg that uses light forces, round wires and modified ribbon-arch attachments.

Beilby layer Eponym for the molecular disorganized surface layer of a highly polished metal. A relatively scratch free microcrystalline surface produced by a series of abrasives of decreasing coarseness.


first order Offsets in the archwire to accommodate the labiolingual and buccolingual thickness of teeth or to produce horizontal forces.

second order Offsets in the archwire in the vertical plane that are used for tipping and/or uprighting teeth.

third order A twist in a rectangular archwire along its long axis that produces torque.

gable, tent bends Bends to upright teeth at extraction sites.

"V" bends Place to mark, solder or twist wire or activate tooth movement.

Bennett movement (Sir Norman G. Bennett 1870-1947) Lateral translation (sideshift) of the working condyle during lateral excursions.

beta-titanium A bcc allotropic form of titanium alloy comprising of titanium, molybdenum, vanadium and trace elements. Beta titanium alloys have a strength/modulus of elasticity ratios almost twice those of 18-8 austenitic stainless steel, larger elastic deflections in springs, and reduced force per unit displacement 2.2 times below those of stainless steel appliances. The titanium alloys have good formability and can be easily welded.

bialveolar protrusion Anterior protrusion limited to the teeth and their alveolar processes.

bilateral Relating to both sides (of the body).

Bimler appliance A modification of the removable activator functional appliance.

biologic width The combined width of connective tissue and junctional epithelial attachment adjacent (part of the gingival complex) to a tooth and superior to the crestal bone.

biomechanics The study of mechanical principles applied to biological functions; the application of mechanical laws to living structures; the study and knowledge of biological function from an application of mechanical principles.

bionator A modified removable functional appliance, developed by Balters to provide better control of the buccal musculature than some other functional appliances.

biostatistics The science of the application of statistical methods to biological facts, as in the mathematical analysis of biological data.

bisphosphonates (also called diphosphonates) are a class of drugs that inhibit osteoclast action and the resorption of bone. Its uses include the prevention and treatment of osteoporosis, ostetis deformans, bone metastasis (witth or without hypercalcemia), multiple myeloma and other conditions that feature bone fragility.

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 Certification An examination program that establishes the clinical competency of a dental specialist according to the procedures established by the individual specialty certification board under the rules and authority of the Council on Dental Education of the American Dental Association. The recognized board in the specialty of orthodontics and dentofacial orthopedics is The American Board of Orthodontics.

Board Certified The status of an orthodontist who has successfully completed all three phases of the certification process administered by The American Board of Orthodontics.

Board Diplomate An orthodontist who has successfully completed all three phases of the certification process administered by The American Board of Orthodontics.

Board Eligible The status of a dental specialist whose educational qualifications have been verified by acceptance of an application for certification by the recognized certifying board and who has passed an initial written examination. Board eligibility is dependent on advanced education in the specialty and on timely progress toward completion of the certification procedure.

bodily movement Translational movement of a tooth or dental segment, ordinarily understood to be perpendicular to the long axis/axes.

Bolton analysis A method developed by Wayne Bolton for the evaluation of tooth-size discrepancies (mesiodistal crown diameter) between the maxillary and mandibular arches.

Bolton Point A landmark, as viewed on the lateral cephalometric film; the highest point on the averaged outlines of the retrocondylar incisures of the occipital bone. It approximates the antero-posterior center of the foramen magnum. It was named in honor of Charles B. Bolton, a patron of the pioneer cephalometric researcher, B. Holly Broadbent Sr.

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 en masse to the mouth by means of a molded matrix that preserves their predetermined orientation and permits them to be bonded simultaneously.

braces See fixed appliance.

brachycephalic Cranial form characterized by a large width (broad head). The cephalic index is greater than 81.0; the opposite of dolichocephalic.

brachyfacial (brachyprosopic) A facial pattern characterized by a broad, square face; preferred term is euryprosopic.

brazing A joining process wherein coalescence is produced by heating to suitable temperatures above 800oF and by using a non-ferrous filler metal having a melting point below that of the base metals. The filler metal is distributed between the closely filled surfaces of the joint by capillary attraction. See also soldering.

bruxism 1. the parafunctional grinding of teeth. 2. an oral habit consisting of involuntary rhythmic or spasmodic nonfunctional gnashing, grinding or clenching of teeth, in other than chewing movements of the mandible, which may lead to occlusal trauma, attrition of the teeth, muscle ischemia, pain and damage to the supporting tissues. It is also called tooth grinding or occlusal neurosis.

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.

buccal Toward the cheeks.

buccoversion Buccal malposition of a tooth or groups of teeth.

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canine guidance A form of mutually protected articulation in which the vertical and horizontal overlap of the canine teeth disengage the posterior teeth in lateral excursive movements. Also called canine protected occlusion.

capitation dentistry A capitation dental program is one in which a dentist or dentists contract with the program's sponsor or administrator to provide all or most of the dental services to subscribers who are covered under the program in return for payment on a per capita basis.

cast (dental) A plaster replica (plaster model) of the teeth and surrounding tissues, typically made from an alginate impression and used for diagnosis, treatment planning and appliance fabrication. It is a part of the patient's permanent record.

cast (metallurgical) To produce a shape by thrusting molten liquid or plastic material into a mold possessing the desired shape. Used to make cast appliances, brackets etc.

CBCT Abbreviation for Cone Beam Computed Tomography.

CDABO See College of Diplomates of the American Board of Orthodontics.

center of resistance The center of resistance (CR) of a tooth is the point of concentrated resistance to movement. A force that acts on a body at CR causes a tooth to translate in the direction of the line of force without rotation. The center of resistance can be considered an area rather than a point in three dimensions. In free space, the CR is the center of the tooth which happens to correspond to the center of gravity of the tooth.

center of rotation The point about which a body appears to have rotated in a nontranslational plane (two-dimensional) displacement.

centric occlusion Mandibular position dictated by maximum and habitual intercuspation of the maxillary and mandibular teeth; variously referred to as intercuspal position, habitual centric, usual occlusal position. The condylar position may or may not be in harmony with centric relation. Because of this, the term habitual occlusion is preferable. Historically, a gnathologic and articulator oriented term.

centric relation A gnathologic term that denotes optimal condyle-articular eminence-glenoid fossa relationships, determined by muscle balance and independent of tooth intercuspation. Changing concepts no longer accept the most retruded, rearmost or hinge axis definition, originally derived from prosthetic articulators. To the orthodontist, the condylar position can vary somewhat, but is generally recognized as high on the posterior surface of the articular eminence. Lack of harmony of centric occlusion and centric relation status is particularly important in diagnosis of TMJ problems.

cephalic index The ratio of the maximum width of the head to its maximum length (i.e., in horizontal plane), sometimes multiplied by 100 for convenience. The head shape can be characterized as either dolichocephalic (long headed), mesocephalic (moderate headed), or brachycephalic (broad headed).

cephalogram A term used as a synonym for cephalometric radiograph.

cephalometer An instrument developed from the anthropologic cephalostat, used now on patients to obtain standardized and oriented craniofacial images on radiographic film. The design of the instrument permits longitudinal study with minimal positional and magnification error.

cephalometric analysis The process of evaluating dental and skeletal relationships by way of measurements obtained directly from the living head or, more commonly, from cephalometric radiographs and tracings. Refers also to the standardized sets of cephalometric measurements (e.g., Downs Analysis) commonly used in the evaluation.

cephalometric landmarks Points on a cephalometric radiograph or tracing representing certain hard or soft tissue anatomical structures (anatomical landmarks) or intersections of lines (constructed landmarks).

A point Subspinale (Downs) The deepest (most posterior) midline point on the curvature between the ANS and prosthion.

ANS anterior nasal spine The tip of the bony anterior nasal spine at the inferior margin of the piriform aperture, in the midsagittal plane.

AR articulare A (Bjork) constructed point representing the intersection of three radiographic images: the inferior surface of the cranial base and the posterior outlines of the ascending rami or dorsal contour of the mandibular condyles bilaterally.

B point (Downs) The deepest (most posterior) midline point on the bony curvature of the anterior mandible, between infradentale and pogonion. Also called supramentale.

Bolton point (Broadbent) The highest points on the outlines of the retrocondylar fossae of the occipital dome, approximates the center of the foramen magnum.

Co condylion The highest point on the superior outline of the mandibular condyle.

glabella The point between the superciliary arches in the midline.

gnathion The most anterior-inferior point on the chin; a cephalometric landmark in the lateral view.

GO gonion The most posterior inferior point on the outline of the angle of the mandible. In cephalometrics, it is identified by bisecting the angle formed by the tangents to the mandibular corpus (mandibular plane) and posterior border of the mandible (dorsal ramal plane); when both the angles of the mandible appear on the sagittal cephalometric radiograph, a point midway between the right and left side is used.

incision superius Incisal edge of the maxillary incisor.

incision inferius Incisal edge of the mandibular incisor.

infradentale The highest and most forward point of the alveolar process between the mandibular central incisors.

key ridge The most inferior point on the zygomatic process of the maxilla as seen in a lateral cephalometric radiograph; the craniometric point zygomaxillare.

labrale inferior Most forward point of the lower lip.

labrale superior Most forward point of the upper lip.

menton The most inferior point on the chin in the lateral view. A cephalometric landmark.

NA nasion The intersection of the internasal and frontonasal sutures in the midsagittal plane.

OR orbitale The lowest point on the inferior orbital margin.

POG pogonion The most anterior point on the contour of the bony chin in the midsagittal plane.

PO porion The superior surface of the external auditory meatus. In craniometry it is identified as the margin of the bony canal on the skull. In cephalometrics it may be identified from the earpost of the cephalostat (machine porion) or from bony landmarks on the film (anatomical porion).

PNS posterior nasal spine The most posterior point on the bony hard palate in the midsagittal plane; the meeting point between the inferior and the superior surfaces of the bony hard palate (nasal floor) at its posterior aspect.

pronasale Most forward point of the tip of the nose.

prosthion The lowest and most forward point of the alveolar process between the maxillary central incisors.

R point (Broadbent) A cephalometric reference point for registration of superimposed tracings.

S sella turcica The geometric center of the pituitary fossa (sella turcica), determined by inspection – a constructed point in the mid-sagittal plane.

stomion Intersection of the closed upper and lower lips.

subnasale The intersection of the columella of the nose and the upper lip.

Xi point (Ricketts) A constructed landmark on the center of the ramus of the mandible.

cephalometric radiograph A standardized radiograph of the head characterized by a precisely defined relationship among x-ray source, subject and film. By convention, the distance between x-ray source and the 'center' of the subject (midsagittal plane or transporionic axis) is either 5 feet (152.4 cm.) or 150 cm. The distance between the midsagittal plane or transporionic axis of the subject and film is approximately 12 cm, but may be standardized at a different value or varied according to head size and recorded for each exposure. The standard projections are lateral (profile) and posteroanterior (P-A).

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.

ceramic brackets Crystalline alumina tooth-shade or clear synthetic sapphire brackets that are esthetically more attractive than conventional metal attachments.

cervical anchorage See anchorage.

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. The defect can extend into the nares and may involve the alveolar process. It is caused by a defect in the fusion of the maxillary and nasal processes and may be accompanied by cleft palate.

cleft palate A unilateral or bilateral congenital fissure in the palate. It is caused by a failure of the premaxilla and lateral palatine process to fuse and may be accompanied by a cleft lip.

clenching Nocturnal parafunctional activity of temporalis, masseter and pterygoid muscles that is considered to be part of a stress-strain-tension release syndrome, frequently associated with bruxism and temporomandibular joint disturbances.

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.

closing loop An “auxiliary” incorporated into an archwire that, upon mesiodistal-pulling activation (which opens the loop), moves adjacent teeth together.

cold working The process of changing the form or cross-section of a piece of metal at a temperature below the softening or recrystallization point, but commonly at or about room temperature. It includes rolling, drawing, pressing and stretching.

College of Diplomates of the American Board of Orthodontics (CDABO) An organization of orthodontists who are board-certified by the American Board of Orthodontics. Any board-certified orthodontist is eligible to become a member of the CDABO. The purpose of the CDABO is to support, encourage and facilitate the process of board certification for all orthodontists. The CDABO also sponsors cutting edge, family-oriented, continuing education meetings for its members.

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. Treatment may utilize fixed and/or removable orthodontic appliances and may also include functional and/or orthopedic appliances in growing and non-growing patients. Adjunctive procedures to facilitate care may be required. Comprehensive orthodontics may incorporate treatment phases focusing on specific objectives at various stages of dentofacial development.

compressive deformation The shortening of a dimension of a “body” due to a pushing force.

computer-assisted tomography (CATscan) The presentation of anatomical information from a cross-sectional plane of the body by computer synthesis of an image from x-rays. Transmission data is obtained in many different directions through the plane under consideration.

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 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.

condyle The rounded cartilage and bone articulating element of the mandible. The superior portion of the ramus that articulates with the temporal eminence in the glenoid fossa.

condylar displacement A functional abnormality in which one or both mandibular condyles are displaced from their normal relationships with their articular discs and eminentia in the glenoid fossae.

condylar guidance 1. Mandibular guidance generated by the condyle and articular disc traversing the contour of the glenoid fossa. 2. The mechanical form located in the upper posterior region of an articulator that controls movements of its mobile member.

condylar growth Proliferation of condylar cartilage, followed by its endochondral ossification. The condyle is a site of growth that is important to the overall development of the mandible. Condylar growth normally stops shortly after that of the rest of the face, although it may continue well beyond adolescence, particularly in males, or it may stop and begin again.

condylion The highest point on the superior outline of the mandibular condyle.

continuous orthodontic force Action of an appliance against the dentition that decreases little in magnitude during the between-appointments period.

corticotomy In bone surgery, a corticotomy is a cutting of the bone that splits it in two but involves cortex only, leaving intact the medullary vessels and periosteum.. Corticotomy is particularly important in distraction osteogenesis and also where RAP (regional acceleratory phenomenon) is used to accelerate tooth movement.

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

couple A pair of equal and opposite non-collinear forces applied to a body. A couple always results in the creation of a pure moment with a tendency to rotate around the center of resistance.

couple-force ratio The ratio of magnitudes of the crown couple to the crown force, having net units of length (e.g., mm), in the two-dimensional analysis of tooth movement.

coupling Designates the stereotyped sequence of bone resorption- formation within the evolving secondary harvesian systems. It involves the concerted action of the osteoclasts and osteoblasts.

cranial base The inferior part of the skull or the brain case that forms predominantly by endochondral ossification. Because the bones of the cranial base stop growing relatively early, they are often used as a reference in the superimposition of serial cephalograms or tracings to measure changes due to growth, time and treatment.

craniometry The direct measurement of dry skulls; an anthropometric technique that forms the basis of cephalometric radiography.

crepitus A grating or grinding sound in a moving joint or fracture.

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

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.

Crozat appliance A wrought-wire removable orthodontic appliance introduced by George Crozat.

curve of Spee [Ferdinand Graf von Spee (1855-1937)] 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. Also called Anteroposterior curve.

curve of Wilson (George H. Wilson 1855-1922) 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. This imaginary curve which is defined by a line tangent to the buccal and lingual cusps of the mandibular posterior teeth bilaterally, is termed the curve of Wilson. Also called Mediolateral curve.

cyst A sac (normal or abnormal) in bone or soft tissue, usually lined by epithelium and containing a liquid or semisolid material.

- D -

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.

deformation Any change in the geometry (size and/or shape) of a body produced by the application of force.

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.

dentofacial orthopedics A synonym for orthodontics that more fully describes the scope of contemporary practice. See orthodontic.

developmental guidance See guidance.

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.

diarthoses Another term for synovial joints.

diastema A space between two adjascent teeth in the same dental arch.

differential moment The application of different moments to adjacent teeth that create different tendencies to rotate with different equilibrium forces present.

digital image A rectangular array of numbers representing the gray scale of a radiograph or color shades of a color image.

digitization Conversion of any landmark of interest to numerical values on a two or three-dimensional coordinate system. The process allows for automatic measurement of landmark relationships and reduces the human error to landmark identification.

Diplomate A dental specialist who has achieved certification by the recognized certification board in that specialty, as attested by a certificate from the Board. See American Board of Orthodontics.

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.

disclusion Separation of opposing occlusal surfaces as the mandible moves into different functional positions.

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

displacement A movement from the usual place or position.

distal A direction oriented along the dental arch away from the dental midline; right or left in the anterior segment posteriorly in the buccal segments.

distal segment Synonymous with posterior segment.

distoclusion Mandibular teeth occlude posterior to their normal relationship to the maxillary teeth, as in an Angle Class II malocclusion.

distoversion A term sometimes used to describe a tooth positioned distal (posterior) to its normal position.

distraction osteogenesis A surgical technique used for lengthening of bones for the correction of skeletal deformities; in the craniofacial area it is used for the treatment of hypoplasias of the maxilla or the mandible.

DHMO (dental health maintenance organization) A legal entity that accepts responsibility and financial risk for providing specific services to a defined population during a defined period of time at a fixed cost. An organized system of healthcare delivery that provides comprehensive care to enrollees through designated providers. Enrollees are generally assessed a monthly payment for healthcare services and may be required to remain in the program for a specified amount of time. See HMO.

dolichocephalic Long, narrow cranial form (cephalic index 75.9 or less); the opposite of brachycephalic.

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

down-fracture In orthognathic surgery, a procedure in which all or part of the maxillary alveolar or basal bone is separated and/or broken away from the more superior elements of the midfacial skeleton. See Le Fort 1.

Downs analysis A group of ten lateral cephalometric measurements developed by William B. Downs for the purpose of evaluating dentofacial relationships.

drift See mesial drift.

dysfunction Partially impaired or abnormal function.

dysplasia Abnormality in development.

- E -

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

EARR Abbreviation for External Apical Root Resorption.

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

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.

elastic descriptive of material behavior such that, upon unloading from a deformed state, recovery is totally to the configuration prior to loading (adjective). A flexible appliance auxiliary, that exhibits substantial force.

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

elastic deformation A deformation not sufficiently severe to take the most strained element of a body beyond the elastic limit of the material.

elastic limit The limit of load, stress, deformation, or strain beyond which the loaded (activated) body will exhibit permanent deformation (a new passive shape) upon complete unloading (deactivation).

elastic range The deformation or strain coordinate of the elastic limit.

elastic strength The load or stress coordinate of the elastic limit.

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.

electrosurgery The application of a high-frequency electric current to tissue as a means to remove lesions, arrest bleeding, or cut tissue. Electrosurgery can be used to cut, coagulate, desiccate or fulgrate tissue.

embrasure 1. the space formed when adjacent surfaces flair away from one another. 2. in dentistry, it is the space that is formed around the adjoining contact of two teeth.

emergence Coming out of; often used to describe the initial appearance of a tooth as it breaks through the gingival tissue during eruption.

EMG Abbreviation for electromyography.

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.

enucleate A surgical procedure that describes the removal of a complete structure, such as an unerupted tooth or a cyst.

equilibrate To reshape the occlusal (functional) surfaces of the teeth in order to alter the functional relationship, thereby redistributing and balancing the functional load.

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

esthetics, facial See facial esthetics.

etch The application of a weak acidic solution to the labial or lingual surfaces of teeth as part of preparation for bonding orthodontic attachments to the teeth.

etchant An agent that is capable of etching the surface.

etiology The cause of a medical or dental condition.

excessive force Force delivered by an orthodontic appliance that is of such magnitude that it may damage supporting tissue or cause anchorage loss.

exfoliate Physiological loss or shedding, as when a primary tooth is lost prior to the eruption of the permanent tooth.

exostosis An overgrowth of bone which results in a bony projection, as a tori or spur.

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

expansion key An instrument used to turn the “jackscrew” in an expansion appliance.

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

expansion, rapid palatal (RPE) See rapid palatal expansion.

extraction Removal of a tooth.

extraction, serial See serial extraction.

extraoral anchorage Anchorage located outside the mouth.

extraoral force or traction A force that originates outside the oral cavity.

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

- F -

facebow 1. A long metal bow which is used in conjunction with extraoral traction anchored on the back of the head or neck. The metal bow inserts intraorally into an orthodontic appliance and is generally used to distalise teeth or bones or prevent their forward movement. 2. A caliper-like instrument used to record the spatial relationship of the maxillary arch to some anatomic reference point or points and then transfer this relationship to an articulator; it orients the dental cast in the same relationship to the opening axis of the articulator.

facemask The component of an (primarily) extraoral, reverse-pull or protraction appliance that distributes responsive force across much of the face.

facial Of or relating to the face. Often used to identify the surface of a tooth located nearest the face.

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 pattern A term generally used to describe the facial form or the direction and type of facial growth.

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).

faciolingual The local direction perpendicular to the mesiodistal direction and parallel to the occlusal plane; the facial direction/sense is away from and the lingual (or palatal) direction/sense is toward the tongue; labial and facial are synonymous in the anterior portion of the dental arch, and buccal is synonymous with facial in the posterior portions of the dental arch.

fatigue The tendency for a metal to break under conditions of repeated cyclic stressing considerable below the ultimate tensile strength.

fee for service dentistry A method of paying practitioners on a service-by-service basis rather than a salaried or capitated basis.

fenestration A window defect of the gingival tissue or alveolar bone contiguous to the root surface.

fiberotomy A surgical procedure designed to sever the gingival and/or transseptal periodontal fibers around a tooth in an attempt to reduce the tendency for relapse of corrected tooth rotations.

finger spring A configured segment of wire that may be included in an orthodontic appliance or a retainer that, when activated, tips a tooth in a desired direction.

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

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