口腔专业英语词汇

口腔专业英语词汇 - A - A See Point A (subspinale) Acromegaly A disease caused by increased activity of the anterior pituitary 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 orthodontic treatment and retention appliances. Activation The process of deforming an appliance member from its passive state (e.g., the stretching of an elastic)and completing its engagement to produce an intraoral 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 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 appliances by means of point contact with the mesio- and disto-buccal undercuts of individual buccal teeth. Adolescent Dentition The dentition that is present after the normal loss of all primary teeth and PRIOR to cessation of growth that would affect orthodontic treatment. Adult Dentition The dentition that is present after cessation of growth that would affect orthodontic treatment. Alginate An irreversible hydrocolloid consisting of salts of alginic acid (an extract of marine kelp). Used to make impressions for dental casts. 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. American Association of Orthodontists Undefined at the moment American Board of Orthodontics The recognized certifying Board for the specialty of orthodontics. See Board. Analog image Computer entered image obtained directly from a radiograph or photograph before digitization. These images are limited by the resolution of the first image. Anchorage Receptor(s) of responsive force(s) delivered as a result of the activation of an orthodontic or orthopedic appliance; by definition, displacement or deformation of anchorage is generally undesirable. Cervical anchorage Receptor of responsive force, from an activation, (primarily) extraoral appliance, that is the back of the neck. Cranial anchorage Receptor of responsive force, from an activated, (primarily) extraoral appliance, that is the posterior and superior portions of the head. Extraoral anchorage Receptor(s) of responsive force(s), delivered by r an activated, orthodontic or orthopedic appliance, located outside the oral cavity. Intraoral anchorage Receptor(s) of responsive force(s), delivered by an activated orthodontic or orthopedic appliance, located within the oral cavity. Occipital anchorage Receptor of responsive force, from an activated, primarily extraoral appliance, that is the occipital region of the head. Anchorage preparation To place teeth in such a position that if one tooth moves all teeth move in a bodily direction. Andresen appliance See Activator Angle Classification of malocclusion A classic gross classification of malocclusion introduced by Edward H. Angle. The governing criterion is the anteroposterior relationship of upper and lower first molars. Not recognized are the many other serious malrelationships related to the anteroposterior axis, those that are related to the lateral or vertical axis and those among teeth of the same arch. Some of the common orthodontic problems not recognized by the Angle classification include buccolingual crossbites, cuspid relationships, crowding, spacing, missing or impacted teeth, rotations and overbite. "Divisions" are used in Class II, based on inclination of maxillary incisors. "Subdivisions" are used to describe unilateral malocclusion characteristics of the affected posterior segmental relationships. Class I malocclusion A malocclusion in which the mesiobuccal cusp of the maxillary first molar occludes in the buccal groove of the mandibular molar. "Class I" is sometimes incorrectly used as a synonym for normal occlusion, whereas it signifies only a normal sagittal relationship of upper and lower teeth as they meet. Class II malocclusion A distal (posterior) placement of the mandibular (lower) molar, mesial (anterior) relationship of the maxillary (upper), or a combination of the two. The mesiobuccal cusp of the upper first molar occludes mesial to the buccal groove of the lower, usually near the embrasure between the lower molar and second bicuspid. Division 1. A Class II molar relationship with proclined upper incisors with respect to the lower incisors. Division 2. A Class II molar relationship, usually with the upper central incisors tipped lingually, the upper lateral incisors tipped labially, and an excessive overbite. Class III malocclusion Mesial (anterior) relationship of the lower first molar to the upper, a retruded relationship of the upper first molar to the lower, or a combination of the two. The mesiobuccal cusp of the upper first molar will typically occlude near the embrasure between the lower first and second molars. Angle of twist The measure of torsional (third-order) deformation of a shaft or an orthodontic wire. Ankylosis Abnormal immobility, union or fusion. May occur between two bones at their articulation (i.e., TMJ) or between teeth and alveolar bone. In such a 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 continue their normal pattern of eruption. Anodontia Congenital absence of teeth. 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 Selia Turcica and Nasion. Anterior Nasal Spine Pointed bony process at the inferior margin of the piriform aperture. 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. Apical Base Maxillary and mandibular bone that supports and is continuous with the alveolar processes; (also see basal bone). Although the demarcation between alveolar and basal bone is not specific, it is generally thought to lie at the level of the apices of the roots. 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. Orthodontic appliance Any device use to influence the growth or position of teeth. Removable appliance An appliance not fixed 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) Arch Collectively, the teeth or basal bone of either jaw. Alveolar Arch The U-shaped alveolar bone that surrounds the dentition of either jaw. Dental Arch The arcade of teeth in either jaw. Basal Arch The U-shaped basal bone of either jaw. Arch form The shape of an individual dental arch or of an arch wire (qv) formed to fit or shape that arch. Arch length A measurement of available and required space needed to align the teeth. Arch length deficiency Difference between available and required space to align the teeth. (See Discrepancy) Arch wire or archwire A wire engaged in orthodontic attachments, affixed to the crowns of two or more teeth, and capable of causing or guiding tooth movement. Continuous arch wire 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 arch wire An arch wire that engages, through crown attachments, only a few teeth (e.g., only the four incisors or only a posterior dental segment) Articulare The point of intersection of the dorsal contour of the mandibular condyle and the temporal bone, as viewed on the lateral cephalometric film. (Bjork) ASCII American Standard Code for Information and Interchange is one of the standard formats for representing characters. It is useful when files are shared between programs. A text file is in ASCII format. Available energy Energy retained in a body owing to existing deformational or thermal constraints that, upon release of the constraints, would be transferred from the body and could be controlled to produce a desired effect. 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. - B - B See Point B Balancing Side A term used for 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. 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. Basal Bone The bone that underlies, supports, and is continuous with the alveolar process (also see epical 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, round wires and modified ribbon-arch attachments. Bends First order Offsets in the arch wire to accommodate the labiolingual and buccolingual thickness of teeth. (horizontal plane) Second order Offsets in the archwire in the vertical plane for tipping and uprighting teeth. Third order Twist or torque changes in a rectangular arch along the long axis of the archwire. Tip-back bends Bend placed to tip teeth back. Tip-forward bends Bend's placed to tip teeth forward. Gable, tent bends Uprighting teeth at extraction sites. "V" bends Place to mark, solder or twist wire. Aesthetic bends (beauty) Positioning anterior teeth for optimal cosmetic appeal. Bennen Movement Lateral translation (sideshift) of the working condyle during lateral excursions. Bimaxillary protrusion Anterior (protrusive) position of both jaws in relation to other cranial and facial structures. Considered archaic or confusing. Bimaxillary Dentoalveolar Protrusion Bimaxillary protrusion limited to the teeth and alveolar processes. Bimler Appliance A modification of the removable activator functional appliance. Bionator A modified removable functional appliance, developed by Baiters to provide better control of the buccal musculature. BIOS The Basic Input/Output System or the part of the computer operating system that communicates with the screen, the keyboard, printers, and other peripheral devices. Bit A binary digit is the smallest storage unit for data in a computer. Biteblock An upper or lower removable appliance, usually covering the occlusal surfaces of the teeth, used for vertical control or in TMD problems. Biteplate or bite plane A removable orthodontic appliance designed to open the bite and/or prevent selected teeth from occluding. Bitwise A bitwise operation is an operation that is performed on bits, not decimal numbers. Board Certification An examination program that establishes the clinical proficiency of a dental specialist according to the procedures established by the individual Specially Certification Board under the rules and authority of the Council on Dental Education of the American Dental Association. The recognized board in the specially of orthodontics is the American Board of Orthodontics. Board Certified The status of a dental specialist who has completed the certification examination of the Certification Board in that special area of practice. Board Diplomate A dental specialist who has achieved certification by the ADA recognized Certifying Board in that specially, as attested by a diploma from that Board. 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 completed an initial written examination. Board eligibility is dependent on advanced education in the specially 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 upper and lower 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 anters-posterior center of the foramen magnum and 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 directly to the teeth by an adhesive. Direct Bonding An intraoral procedure in which orthodontic attachments are oriented by inspection and bonded individually. Indirect Bonding A two-step process by which orthodontic attachments are affixed temporarily to the teeth of a study model 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. 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 in euryprosopic. Bruxism Habitual grinding or gnashing of the teeth, usually during sleep. May cause severe attrition of the teeth, muscle ischemia and pain and damage to the supporting tissues. Frequently associated with clenching and TMD problems. An 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. Buccal Toward the cheeks. Buccoversion Buccal malposition of a tooth or groups of teeth. Buffer A temporary storage area used by computers and some printers. Byte The amount of space needed to store a single character (number, letter, or code). A byte generally represents eight binary digits (bits). For example, if a character requires one byte of storage space, that one byte is translated to eight bits when processed in the computer. 1024 bytes equals one kilobyte (K). - C - 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 br most of the dental services covered under the program to subscribers in return for payment on a per capita basis. Card(computer) A removable printed-circuit board that is plugged into an expansion slot (e.g., graphics card, clock card). 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, and as a part of the patient's permanent record. Center of resistance The point on a body where the entire mass of the body can be considered concentrated. A force acting through the center of resistance causes the body to translate in the direction of the line of force without rotation. Center of resistance A singular point in a body through which the line of action of a resultant force must pass to produce translation of that body. Center of rotation A point around which a body turns in any one of three possible axes as exemplified by the yaw, pitch and roll of a space vehicle. 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 upper and lower teeth; variously referred to as intercuspal position, habitual centric, usual occlusal positron, 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, signifying optimal condyle-articular eminence-glenoid fossa relationships, determined by muscle balance and not by tooth intercuspation. Changing concepts no longer accept the most retruded, rearmost or h*nsze 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 TMD problems. Cephalic index An anthropometric value based on the ratio between the width and length of the head. cephalic index = (maximum head (or skull) width X 100) / (maximum head (or skull) length) Cephalogram A term loosely used as a synonym for cephalometric radiograph: sometimes used to refer to a fine-line tracing on an acetate film overlay of the salient structures, landmarks and pertinent measurements, which is used for diagnostic purposes. However, measurements may be digitized directly from the film via computer. Cephalometer An instrument developed originally from the anthropologic cephalostat, used now on patients to obtain standardized and oriented craniofacial images on X-ray film. The design of the instrument permits longitudinal study with minimal positional and magnification error. (See Cephalostat) 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 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 (1 52.4 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 (see cephalogram) Ceramic brackets Crystalline alumina tooth-shade or clear synthetic sapphire brackets that are esthetically more attractive than conventional metal attachments. Cervical anchorage See definition under 'Anchorage.' Cervical appliance A primarily extraoral appliance that when activated delivers responsive force, distributed by means of a pad, to 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. Caused by a defect in the fusion of the maxillary and nasal processes; 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 lateral shelves 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 sounds emanating from one or both temporomandibular joints, usually due to anterior or anters-medial or anters-lateral displacement of the articular disk during functional movements. Clip-on arches Auxiliary arches clipped to brackets for leveling rotations, and torque; also known as clip arches. Closed bite Excessive vertical overlap of the anterior teeth; deep bite. Closed loop An auxiliary, fabricated of orthodontic wire, prepared such that the two 'legs' of the passive loop contact (exerting mesiodistal force upon) one another. Closing loop An auxiliary fabricated of orthodontic wire that, upon mesiodistal-pulling activation, exhibits a reduction in the plane area enclosed within its geometry. Comprehensive orthodontic therapy The coordinated diagnosis and treatment leading to the improvement of a patient's craniofacial dysfunction and/or dentofacial deformity, including anatomical, functional and esthetic relationships. Treatment usually, but not necessarily, utilizes fixed orthodontic appliances. Adjunctive procedures such as extractions, maxillofacial surgery, nasopharyngeal surgery, myofunctional or speech therapy and restorative or periodontal care, may be coordinated disciplines. Optimal care requires long-term consideration of patients' needs and periodic reevaluation. Treatment may incorporate several phases with specific objectives at various stages of dentofacial development. Compressive deformation The shortening of a characteristic dimension of a body associated with 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 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 elimination of the radiograph with a much wider dynamic range for improved edge enhancement, and ability to change contrast in specific regions. Concentrated force An external contact force with the area of contact very small compared to the total surface area of the body subjected to the force. Condyle The rounded cartilage and bone articulating element. in 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 disks and eminentia in the glenoid fossae as the mandible is brought into habitual occlusion. Condylar guidance The functional movements of the mandible as determined by the morphology of the mandibular condyles and articular disks and eminentia in the glenoid fossae.' 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. Cosmetic orthodontics Orthodontic therapy whose purpose 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. Mechanical couple A pair of concentrated forces having equal magnitudes, the same direction but opposite senses, and noncollinear (parallel) lines of action. 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. CPU or Central Processing Unit The portion of the computer which executes the commands of a program and controls the flow of information to and from peripheral devices such as monitors, disk drives and printers. Cranial Base The endochondral bone that forms the anteroinferior aspect of the brain case. Because the bones of the cranial base stop growing relatively early, they are often used in the superimposition of serial cephalograms or tracings. Craniometry The direct measurement of dry skulls; a highly developed 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 a fixed transpalatal tongue and finger interceptive appliance. Crossbite An abnormal relationship of a tooth or teeth to the opposing teeth, in which normal buccolingual or labiolingual relationships are reversed. Crowding Dental malalignment caused by inadequate space for the teeth. Crozat Appliance A wrought-wire removable orthodontic appliance originally introduced by George Crozat, 1920. Crown Lengthening. A periodontal procedure directed at exposing more clinical crown by managing the soft or hard tissue or both surrounding a tooth. When a tooth has short clinical crowns by excess tissue, or restoration whose faulty margins extend deep below the gingival margin, or decay extending deep within the soft tissue or even extending into the bone surrounding the teeth, a crown lengthening will reposition the gum and allow for a proper fitting restoration or crown to be placed in a tooth or series of teeth. Crown Movement The transverse tooth displacement for which the center of rotation coincides with the root apex (or the level of root apices for a multirooted tooth). Cursor Moving pointer on computer screen. Cyst A sac (normal or abnormal) in bone or soft tissue, usually lined by epithelium and containing a liquid or semisolid material. Retained impacted teeth may lead to the development of a progressively expanding cyst. - D - Debanding The removal of cemented orthodontic bands. Debonding The removal of bonded orthodontic attachments. Deciduous Referring to the first(deciduous, primary, baby) dentition. 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 clefting defect in the gingival margin. Dentofacial Deformity Dentofacial malformation 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 Orthodontics) Developmental Guidance See Guidance. Diastema A space between two teeth. Differential-force Pertaining to the distribution of two related forces equal in magnitude (and ordinarily in the same direction, but of opposite sense), over areas of differing sizes, thus yielding unequal average force intensities. Differential moment The application of different moments to adjacent teeth creating 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 specially, as attested by a diploma from the Board. See Board and American Board of Orthodontics. Direction The inclination (angular orientation) of a line with respect to a reference plane. Direction/sense One of two Possible manners describing or measuring distance from a reference- or zero -point along a specific- line; also termed, simply, 'sense' with respect to the reference line or axis. Direct Reimbursement A self funded program in which the individual is reimbursed, based on a percentage of dollars spent for dental care provided and which 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 Arch length deficiency. Disk drive A device which provides data storage via interchangeable (floppy) disks, or fixed (hard) disks. Displacement Any movement of a particle or a body as a whole. 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. Distodusion Lower teeth occluding distal to their normal relationship to the uppers, as in an Angle Class II malocclusion. Distoversion A term sometimes used to describe a tooth positioned distal (posterior) to its normal position. Distributed force A force that involves a substantial portion of the surface area of volume of the body acted upon. DMO (Dental maintenance organization) See HMO 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 price. An organized system of healthcare delivery that provides comprehensive care to enrollees through designated providers. Enrollees are generally assessed a monthly payment for health care services and may be required to remain in the program for a specified amount of time. 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. DOS The Disk Operating System is software that directs the flow of data between disk drives and the computer. Without an operating system, the computer can do nothing. 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. (Le Fort 1) Downs Analysis A set of ten lateral cephalometric measures developed by William B. Downs for the purpose of evaluating dentofacial relationships. Drift A term applied to either a natural developmental phenomenon (mesial drift) whereby the posterior teeth continually move slightly forward as the interproximal surfaces wear or where contiguous teeth are missing and there is movement into that space. Driver A set of commands used to run peripheral devices. For example, PRS files are drivers used to run the printer. Dysfunction Partially impaired or abnormal function. Dysplasia Abnormality in development. - E - Eccentric activation An orthodontic-appliance activation that creates a resultant force against the facial or lingual surface of a crown with a line of action not piercing the long axis of the tooth. Ectopic Located away from normal position; often usedto 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 with a rectangular slot for engagement of an orthodontic wire. The most common appliance in use today. Elastic A flexible appliance element ordinarily activated in two-point extension, that exhibits substantial elastic range (noun); descriptive of material behavior such that, upon unloading from a deformed state, recovery is totally to the configuration prior to loading(adjective). Elastics(rubber bands) Variously used as Class II elastics, Class III elastics, Diagonal elastics, Up-down (vertical) elastics and cross-elastics. 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 arch wire or auxiliary from the bracket-slot. Electronic records Conversion of records to digital format for computerized use, manipulation and storage. Emergence Coming out of; often used to describe the initial appearance of a tooth as it breaks through the gingival tissue during eruption. Energy The capacity of a body to produce an effect. Enucleate A surgical procedure for removal of a complete structure such as an unerupted tooth or a cyst. Equilibrate Reshaping the occlusal (functional) surfaces of the teeth to alter the functional relationship; redistributing and balancing the functional load. Equilibrium forces A pair of equal and opposite forces on adjacent teeth that are not equal and opposite. The magnitude of the equilibrium forces is always proportional to the algebraic sum of the moments present on these two teeth. Eruption Movement of teeth in an incisal or occlusal direction through the supporting bone and gingival tissue into the oral cavity. Esthetics, Facial See Facial Esthetics. Etch The application of a weak acidic solution to the labial or lingual surfaces of teeth as part of the preparation for bonding orthodontic attachments to the teeth. Etiology The cause of a medical or dental condition. Euryprosopic A facial pattern characterized by a broad, square face. Excessive force Force delivered by an orthodontic appliance of such magnitude that it may damage supporting tissue and could lead to ankylosis. Exfoliate Physiological loss or shedding, as when a deciduous tooth is lost prior to the eruption of the permanent tooth. Exostosis An overgrowth of bone which results in a bony projection, as a torus or spur. Expanded memory Lotus lntel Microsoft specification for addressing more that 640K of memory. A special memory board and/or driver is needed to access expanded memory. Expansion Enlargement; often used to describe the mechanical widening of the dental arches. Expansion key An instrument used to turn the jack-screw in an expansion appliance. Expansion screw A mechanical device incorporated in a removable appliance or a fixed appliance used to enlarge the dental arch in some dimension. Expansion, Rapid Palatal (RPE) (listed under R) Extraction Removal of a tooth. Extraction, Serial See Serial Extraction. Extraoral anchorage Anchorage located outside the mouth. Extraoral force or traction Force generated by (elastically) deforming an activating element of an orthodontic or orthopedic appliance, located outside the oral cavity. Extrusion A translational form of tooth displacement with movement occlusally directed and parallel to the long axis. - F - 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. Facemask The component of a (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 rather describing 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. Fee for Service Dentistry A method of paying practitioners on a service-by-service rather than a salaried or capitated basis. Fenestration A window defect of the gingival tissue or alveolar bone over the root surface. Fiberotomy A surgical procedure designed to sever the gingival and/or transseptal periodontal fibers around a tooth usually 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 to, when activated, tip a tooth in a desired direction. Finishing A stage of treatment toward the end of comprehensive orthodontic care in which the teeth are placed in their final detailed position. First-order Pertaining to rotational or vertical tooth movement or displacement potentially visible in an occlusal view. First order rotation A tooth as a whole rotates about an occlusogingival axis. The angulation/orientation of the long axis of the tooth does not change. Fixation Immobilization of the facial bones after a surgical procedure by means of wires, screws, plates, elastics, or splints until the healing process is complete. 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. Flared Teeth A term used to indicate that the anterior teeth are tipped forward of their normal position. Flush Terminal Plane A developmental stage. The normal and desirable relationship of the distal surfaces of the upper and lower second deciduous molars. Font A specific typeface, point size, and weight (e.g., 10 pt Helvetica Bold). Force A mechanical action of one body on another that tends to displace and/or deform the body receiving it. Force may be continuous, intermittent, interrupted, intraoral, extraoral, orthodontic, orthopedic, elastic, spring, magnetic, etc, depending on the motivating elements involved. Fossa, Glenoid See Glenoid Fossa. Franchise Dentistry A system for marketing a dental practice, usually under a trade name, where permitted by state laws. In return for a financial investment or other consideration. Participating dentists may also receive the benefits of media advertising, a national referral system and financial and management consultation. Fr?nkel Appliance An activator type appliance intended to stimulate or inhibit jaw growth, retrain muscles or widen the dental arches. Free-way Space The clearance or interocclusal distance between the upper and lower teeth when the mandible is in the 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 connecting lip, cheek or tongue to the alveolar mucosa. (May be labial or lingual.) Friction A resistance to the relative displacement of contacting bodies in a direction tangent to the plane of contact, owing principally to surface roughness and contact pressure. Frontal cephalometric radiograph A radiograph taken with the x-ray source located behind the head and the x-ray film located in front of the face taken according to cephalometric conventions. More correctly termed a posters-anterior (P-A) cephalometric radiograph; see cephalometric radiograph. Full Treatment Comprehensive orthodontic treatment usually involving upper and lower dental arches. Functional Appliance A term applied to a class of removable appliances which utilize the muscle action of the patient to produce orthodontic or orthopedic forces. Functional jaw Orthopedics That form of therapy usually with activator-type appliances, that utilizes the musculature to create dentofacial changes. 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. - G - General Dentist A practitioner who has graduated from dental school and obtained a license to practice general dentistry. Because education in special areas of dentistry is limited in dental school, a general dentist cannot claim to be a specialist. Generalized rotation A whole body, nontranslational displacement characterized by a center of rotation not coincident with the center of resistance of the body. Genial Pertaining to the chin. Genioplasty A surgical procedure designed to reshape the contour of the chin, usually by augmentation or reduction. Gingiva The tissue that surrounds the teeth, consisting of a fibrous tissue that is continuous with the periodontal ligament and mucosal covering. Gingival graft A surgical procedure usually performed to establish an adequate amount of attached gingiva around a tooth or group of teeth. Gingival Attachment The fibrous attachment of the gingiva to the teeth. Gingivitis Inflammation of the gingiva. Glenoid fossa The depression or fossa in the temporal bone in which the condyle of the mandible is positioned; part of the temporomandibular joint (TMJ). Global reference frame A framework of three mutually perpendicular, intersecting lines with which to reference measurements within a dental arch as a whole or the dentofacial complex at large. Glossotomy A surgical procedure involving excision of part of the tongue, designed to reduce tongue size and to change its shape. Gnathion The most anterior-inferior point on the chin; a cephalometric landmark in the lateral view. Gnathology The study of the functional and occlusal relationships of the teeth as they relate to the TMJ; sometimes also used to identify a specific philosophy of occlusal function and treatment or articulator simulation of these movements. Gonial Angle The most postero-inferior point on the angle of the mandible, where t ' he body and ramus join in the region of the attachment of the masseter muscle. (Gonion) Graft A portion of tissue used for implantation. Grinding Usually a term synonymous with bruxism. Growth An increase in size. 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/or the effects of treatment. Growth Potential Generally an estimation of the amount of growth yet to occur. Growth Site An area where a large amount of growth occurs. Growth spurt An increase in rate of growth (velocity) during adolescence, generally of the bones; usually occurring at age 10-12 in the female and 12-14 in males coincident with the events of puberty. Guard, mouth Listed under mouth guard. Guidance, condylar See condylar guidance. 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. General Dentist A practitioner who has graduated from dental school and obtained a license to practice general dentistry. Because education in special areas of dentistry is limited in dental school, a general dentist cannot claim to be a specialist. Generalized rotation A whole body, nontranslational displacement characterized by a center of rotation not coincident with the center of resistance of the body. Genial Pertaining to the chin. Genioplasty A surgical procedure designed to reshape the contour of the chin, usually by augmentation or reduction. Gingiva The tissue that surrounds the teeth, consisting of a fibrous tissue that is continuous with the periodontal ligament and mucosal covering. Gingival graft A surgical procedure usually performed to establish an adequate amount of attached gingiva around a tooth or group of teeth. Gingival Attachment The fibrous attachment of the gingiva to the teeth. Gingivitis Inflammation of the gingiva. Glenoid fossa The depression or fossa in the temporal bone in which the condyle of the mandible is positioned; part of the temporomandibular joint (TMJ). Global reference frame A framework of three mutually perpendicular, intersecting lines with which to reference measurements within a dental arch as a whole or the dentofacial complex at large. Glossotomy A surgical procedure involving excision of part of the tongue, designed to reduce tongue size and to change its shape. Gnathion The most anterior-inferior point on the chin; a cephalometric landmark in the lateral view. Gnathology The study of the functional and occlusal relationships of the teeth as they relate to the TMJ; sometimes also used to identify a specific philosophy of occlusal function and treatment or articulator simulation of these movements. Gonial Angle The most postero-inferior point on the angle of the mandible, where t ' he body and ramus join in the region of the attachment of the masseter muscle. (Gonion) Graft A portion of tissue used for implantation. Grinding Usually a term synonymous with bruxism. Growth An increase in size. 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/or the effects of treatment. Growth Potential Generally an estimation of the amount of growth yet to occur. Growth Site An area where a large amount of growth occurs. Growth spurt An increase in rate of growth (velocity) during adolescence, generally of the bones; usually occurring at age 10-12 in the female and 12-14 in males coincident with the events of puberty. Guard, mouth Listed under mouth guard. Guidance, condylar See condylar guidance. 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. - H - Habit Generally applied in a negative sense to frequently repeated activity such as finger or lip sucking or tongue thrusting. Such activity may alter the normal development of the teeth or bones. Habit Therapy Treatment designed to prevent potentially deforming finger, lip or tongue habits and/or correct a malformation of the teeth or bones caused by a habit. Treatment might occur by counseling or by appliance therapy or both. Habitual occlusion The usual intercuspation position of the teeth which may or may not coincide with centric occlusion or centric relation. Hand-wrist X-ray An x-ray of the carpal, metacarpal and phalangeal bones of the hand and wrist used to determine the progress of the individual toward maturity (bone age or developmental age). Hardening heat treatment A heat-treatment process designed to increase the surface hardness and, perhaps, to suitably affect other properties of a material. Hawley retainer A removable plastic and wire appliance used to stabilize the teeth but often modified for special applications. Headcap The component of a (primarily) extraoral appliance that distributes and transfers responsive force to the cranium. Headgear Common generic term for extraoral traction and anchorage. Health Maintenance Organization (HMO) See DMO 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 price. An organized system of healthcare delivery that provides comprehensive care to enrollees through designated providers. Enrollees are generally assessed a monthly payment for health care services and may be required to remain in the program for a specified amount of time. Heavy force Orthodontic force induced by appliance members exhibiting relatively high characteristic stiffness(es). Herbst Appliance Fixed or removable appliance designed to effect an orthopedic change of the mandible much like an activator. The appliance obliges the jaw to function in an anterior position to stimulate sagittal correction of Class II malocclusions. High angle case A general term applied to a craniofacial pattern whose growth is more vertical than normal; more specifically, a patient with an unfavorable angle of the lower border of the mandible. (See Hyperdivergent) High-pull headgear A (primarily) extraoral appliance that transmits force to a facebow, J-hooks, or chin cap such that, from a sagittal perspective, the cited force includes a superiorly directed component. HMO (See Health Maintenance Organization) Hinge axis The axis of mandibular rotation in the initial opening movement; usually passing through the mandibular condyles; in gnathologic terms, the most retruded position of the condyle in the glenoid fossa, from which functional movements initiate. Holding arch See lingual arch. Hookean Refers to a (crystalline) material for which, on a per-unit-volume basis, force and associated deformation are proportionally (linearly) related within virtually the entirety of the elastic range of the material; Hooke's law: The ratio of mechanical stress to mechanical strain is a constant, an elastic modules of the material. Hooks Attachments soldered or welded to arch wires for the placement of elastics, headgear, or elastic chains. Hygienist(dental) A dental auxiliary person who has been trained in an approved course in Dental Hygiene and is licensed to provide dental hygiene services. Hyperdivergent A facial pattern which includes a high angle of the mandibl4e, possibly a prognathic maxilla, a retrognathic mandible, tendency to open bite, lip incompetence and often a long, sloping forehead. Hyperplasia Tissue enlargement through multiplication of cells, often a response to inflammation or drugs. Hypertrophy An increase in tissue bulk through an increase in size of the tissue elements. Hypodivergent A facial pattern characterized by a low mandibular plane angle, generally favorable horizontal skeletal relationships, maxillary retrusion, deep overbite of the incisor teeth, a prominent chin, a short nose and a straight or concave profile. Hypodontia The inborn absence of one or more teeth. Hypoplasia Incomplete development of a tissue or structure. - I - Iatrogenic An unfavorable response induced by a therapeutic effort. Ideal occlusion A theoretical placement of the teeth in the dental arches which maximizes esthetics function, stability and longevity of the dentition and supporting structures. ldiopathic Caused by unknown factors. Imaging The process of acquiring representations of structures in either two or three dimensions. immobilization To fix in place so that no possible. Usually used in regard to orthognathic surgery. Impaction (tooth) A condition describing the total or partial lack of eruption of a tooth well after the normal age for eruption. An impacted tooth may appear blocked by another tooth, bone or soft tissue, but the cause of tooth impaction if often unknown. Impaction (surgical) A term usually used to describe orthognathic surgery involving the superior repositioning of the upper jaw. (Le Fort 1) 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. Incisal Pertaining to the cutting edge of the anterior teeth. Inclination The angle of the long axis of a tooth from a particular line of reference; the tilt or tip of a tooth. Inclined plane An acrylic ledge or platform which is usually added to a maxillary Hawley retainer and is designed to intrude teeth or to position the lower jaw forward. Indirect bonding A process for bonding orthodontic attachments to the teeth. A laboratory process is performed to position the attachments on plaster casts; the prepositioned attachments are then bonded to the teeth utilizing an elastic impression tray as a transfer device. Individual Practice Association (IPA) A partnership, corporation or other legal entity which contracts with an HMO, union or other provider to provide care to an enrolled group for a fixed monthly amount. In the IPA, the provider can work from his office instead of an HMO center or clinic. Fee-for-service patients can be treated alongside those in the IPA plan. Patients in the IPA plan must use a participating provider. The provider must follow IPA practices, accept reimbursement as full payment and comply with IPA peer review 'and quality assurance procedures. Typically, the IPA pays the provider a percentage of his fee, with the remaining percentage held in a reserve pool that may be divided at year's end by the provider if any funds remain. Inelastic deformation Deformation of a member sufficiently substantial to exceed the elastic limit of the material and, upon total unloading (deactivation), resulting in a 'permanent set' (a change in geometry/shape from the passive state prior to the deformation). Infection control An important aspect of any health service, following guidelines set by CDC, OSHA, etc. Infradentale The highest and most forward point of the alveolar process between the mandibular central incisors. Intraocclusion A tooth or teeth positioned below the normal plane of occlusion. In-out Tooth Position Faciolingual relationships of the teeth to the plane of occlusion. Facial or lingual placement of the labial surfaces of the crowns of the teeth. Intensifying screen A stiff sheet of plastic impregnated with a material which fluoresces when exposed to x-radiation. It is used in an x-ray cassette to intensify the x-ray image and reduce the patient's exposure to radiation. (See rare earth screen) interceptive Orthodontics An extension of preventive orthodontics that may include localized tooth movement in an otherwise normal dentition. Such treatment may occur in the primary or transitional dentition and may include such procedures as the redirection of ectopically erupting teeth, correction of isolated dental crossbite or recovery of recent minor space loss where overall space is adequate. The key to successful interception is intervention in the incipient stages of a problem to lessen the severity of the malformation and eliminate its cause. The presence of complicating factors such as skeletal disharmonies, overall space deficiency, or other conditions requiring present or future comprehensive therapy are beyond the realm of interceptive therapy. Early phases of comprehensive therapy may utilize some procedures that might also be used interceptively in an otherwise normally developing dentition, but such procedures are not considered interceptive in those applications. Intercuspation The relationship of the upper and lower posterior teeth with regard to the placement of cusps in opposing tooth fossae. Interdental spacing Spacing between the teeth. Interdigitation intercuspation. Intermaxillary Between the upper and lower jaws. lntermaxillary anchorage Using one dental arch as anchorage to apply traction on the other dental arch. Intermaxillary elastic traction Use of elastics to apply traction between the upper and lower jaws. Intermittent force An active, orthodontic force that decays to zero magnitude, or nearly so, prior to the end of a between-appointments period. internal derangement An intracapsular problem of the TMJ which may relate to arthritis, fibrosis, tumors, condylolysis, condylar hyperplasia or other internal factors. This condition often reflects a displacement or malrelation of the articular disk to the condyle and articular eminence. Interocclusal clearance Synonymous with freeway space. Interproximal stripping of enamel (slenderizing) Reduction of interproximal width of a tooth by removal of a portion of the enamel (generally anterior teeth) to correct tooth size discrepancies or to enhance post-treatment stability. Interrupted force An orthodontic or orthopedic force that is inactive for intervals of time during the between-appointments period, often exhibiting a cyclic, long-term, magnitude-time pattern (e.g., force exerted by an extraoral appliance worn only at night). Intramaxillary Within one dental arch. Intramaxillary anchorage A situation where a tooth or group of teeth provides anchorage to apply traction to other teeth within the same arch. Intraoral anchorage Anchorage located inside the mouth. Intraoral force Force which is generated by orthodontic appliances in the oral cavity. Intrusion A translational form of tooth movement directed apically and parallel to the long axis. Invisalign?is the invisible way to straighten teeth without braces. Invisalign?uses a series of clear removable aligners to straighten teeth without metal wires or brackets. Invisalign?has been proven effective in clinical research and in orthdontic practices nationwide. You wear each set of aligners for about 2 weeks, removing them only to eat, drink, brush, and floss. As you replace each aligner with the next in the series, your teeth will move - little by little, week by week - until they have straightened to the final position your dentist has prescribed. You'll visit your dentist about once every 6-12 weeks to ensure that your treatment is progressing as planned. Total treatment time averages 9-18 months and the average number of aligners worn during treatment is between 18 and 38, but both will vary from case to case. Invisible braces A lay term applied to orthodontic appliances which are fixed to the lingual surfaces of the teeth composed of transparent or translucent brackets. IPA (individual Practice Association) A legal entity organized and operated on behalf of individual participating dentists for the primary purpose of collectively entering into contracts to provide dental services to enrolled populations. Dentists may practice in their own offices and may provide care to patients not covered by the contract . as well as IPA patients. Irregularity Index An assessment of the crowding of the anterior teeth. - J - 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. Jackscrew Synonymous with expansion screw. 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 anters-posterior or transverse assessment. Joint noise A generalizing term which relates to clicking and crepitus emanating from the TMJ. Joint symptoms A generalizing term referring to various aspects of TMJ dysfunction, internal derangement or other conditions involving the TMJ. Joint, Temporomandibular See Temporomandibular joint. Jumping the bite The correction of a crossbite brought about by horizontal movements of teeth and, occasionally, the jaw, to their correct position. Jumper A spring appliance attached to fixed appliances to move teeth similar to a Herbst appliance. - K - Keyboard A device used to enter data. It is similar to a typewriter keyboard, but has special function keys and a calculator-style keypad that doubles as directional arrow keys for cursor control. Key Ridge The most inferior point on the zygomatic process of the maxilla as seen in a lateral cephalometric radiograph; the craniometric point zygomaxillare. Kinematics That phase of mechanics which deals with possible motions of a body. Kilobyte 1024 bytes of information or storage. Kloehn headgear A (primarily) extraoral appliance defined by a facebow delivering active force bilaterally to the maxillary terminal molars and with responsive force transmitted to the back of the neck. Kyphosis A front-to-back curvature or bending of a bone; often used to describe the anteroposterior curvature of the spine or bending of the cranial base. Kelvin (k) SI unit of temperature defined as the fraction 1/27316 of the temperature of the triple point of water. The temperature in Kelvin is equal to a Celsius temperature plus 273 15?C. Kennedy bar That part of a partial prosthesis consisting of a narrow bar lying in contact with the lingual surfaces of mandibular incisors, which connects the saddles and may provide indirect retention. Kennedy classification A method of classifying partially edentulous mouths and the partial dentures required to restore these edentulous areas. It is based on the location of the edentulous area relative to the remaining teeth. kerat? (kerato?) Prefix denoting: 1. Horny skin or tissue. 2. The cornea. keratin Insoluble protein present in the epidermis, horny tissues and the organic matrix of tooth enamel. keratinized That part of the surface tissue which has become hardened or horny by the formation of keratin. keratoconjunctivitis Inflammation of the conjunctiva and cornea. See Sjogren's syndrome keratogenesis Formation of keratinized - L - 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. Labial arch or bow A wire that traverses the labial surfaces of the teeth. Labial frenum The band of fibrous tissue that passes from the upper or lower lip to the alveolar mucosa, usually inserting in the alveolar process between the upper and lower central incisors. Labial sulcus The furrow that lies between the lips and the alveolar process. Labial root (lingual crown) torque The third-order couple of a transverse force system applied to the crown(s) of a tooth or dental segment having the potential for rotational displacement resulting in labial movement of the root(s) and/or lingual movement of the crown(s). Labiolingual Appliances A fixed orthodontic appliance that includes both facial and lingual crown attachments and archwires. Labioversion General term indicating the deviation of a tooth toward the labial. Labrale inferior Most forward point of the lower lip. Labrale superior Most forward point of the upper lip. Laminography Tomography: i.e. sectional radiography. Landmarks, cephalometric Anatomic and constructed measurepoints used in analysis of cephalometric radiographs. Laser An acronym for light amplification by stimulated emission of radiation. A device utilizing natural oscillation of atoms or molecules between energy levels for generating coherent electromagnetic radiation in the ultraviolet, visible or infrared regions of the spectrum. Laser scanner A laser beam passed through each pixel of a radiograph or picture to measure the amount of transmitted light. This requires a conventional radiograph and is limited by the small dynamic range of radiographic film. Lateral cephalometric radiograph An x-ray taken according to cephalometric conventions with the x-ray source facing the right side of the face and perpendicular to the mid sagittal plane. The ' x-ray film faces the left side of the face. This radiograph is used to measure and determine craniofacial relationships: see cephalometrics. Lateral excursion Movement of the lower jaw away from the middle position. Lateral (external) Pterygoid muscles A group of muscles which are part of the muscles of mastication. They connect from the base of the skull to the condyle of the mandible and assist in protruding and opening the lower jaw. Leeway space The difference between the combined widths of the three buccal deciduous teeth (canine and two molars) and their permanent successors (canine and two premolars.) The average value is 1.0 mm. on each side in the upper jaw and 1.7 mm. on each side in the lower jaw, with wide individual variations. This space' is normally closed by mesial drift of the first permanent molars as the deciduous teeth are replaced. Le Fort Surgical Procedure Surgical procedures 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 procedure in which the maxillary dentition and supporting alveolar process are repositioned on their bony base. Le Fort II Surgical Procedure A procedure, also referred to as a pyramidal fracture, in which the maxillae are separated from their base at the junction of the nasal and frontal bones, through both orbital rims, leaving the lateral orbital rims and nasal processes intact. Le Fort III Surgical Procedure A procedure in which the entire facial bone complex is separated from the cranial base. Leveling The initial phase of comprehensive orthodontic treatment using fixed appliances designed to change the line of intercuspation from a curve to a straight line; to align the teeth in the same plane. Leveling wire Orthodontic wire, ordinarily round (in cross-section) and exhibiting low flexural stiffness, used in the leveling phase of treatment. Ligament, periodontal (Listed under P.) Ligature Typically of annealed wire, rubber, or a polymer, a tie that secures the archwire in the bracket-slot. Light force Orthodontic force produced by an appliance element having relatively low characteristic stiffness(es). Light-wire technique An orthodontic-treatment philosophy or modality within which the appliance components to be activated are relatively flexible, resulting in relatively small force values, active over long time periods. Limited Treatment Orthodontic treatment with a limited objective, not 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 more comprehensive 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 surface of the teeth. Lingual arch A single orthodontic wire usually located in the lower arch traversing 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. Lingual frenum A band of fibrous tissue connecting the tongue with the floor of the mouth and alveolar mucosa, often inserting into the alveolar process. When short it may cause a tongue-tied condition and difficulties with speech. Lingual Retainers A variation of the lingual arch traversing the lingual surfaces of the lower teeth between the cuspids. The purpose is to stabilize the teeth. Lingual root (labial crown) torque The third-order couple of a transverse force system applied to the crown(s) of a tooth or dental segment having the potential for rotational displacement resulting in lingual movement of the root(s) and/or labial movement of the crown(s). Lingual Version Denotes malposition of one or more teeth to the lingual; same as linguoclusion. Linguoclusion An occlusal relationship in which the position of one or more teeth is abnormally lingual. Affected teeth must be identified when this term is used. Lip bumper An appliance designed to eliminate excessive lip pressure on the anterior teeth and transfer that force to the molars instead. Typically, it consists of a labial archwire with an anterior plastic pad, fitted into orthodontic attachments on the molars. The treatment objectives are to allow incisors to move forward and to distalize the molars, increasing the arch length. Lip, cleft see cleft lip. Lip incompetence A gap between the related upper and lower lips because of a vertical hard and soft tissue imbalance. Local reference frame A framework of three mutually perpendicular, intersecting lines with which to reference measurements pertaining to a single tooth or an anterior or posterior dental segment; the mesiodistal and faciolingual directions vary with (local) position around the dental arch. Long-face syndrome A craniofacial syndrome 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. Loops Open loops Loops which open at the base when activated. Closed loops Loops which remain closed at the base when activated (reverse loops). Omega loop A short loop used as a tie back or to activate loops. Long-axis rotation A nontranslational tooth movement characterized by the coincidence of the long axis and the axis of rotation. 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. - M - Macrodontia Teeth that are larger than normal. Magnetic force Repelling and attracting forces created by small rare earth magnets, incorporated in fixed and removable orthodontic appliances to cause changes in tooth position or optimize response in functional magnetic growth guidance appliances. MRI (Magnetic Resonance Imaging) Creation of images of objects such as the body by use of nuclear magnetic resonance phenomenon. Involves imaging the distribution of hydrogen nuclei (protons) in the body. Does not employ radiation. Mal- Prefix denoting a bad or unfavorable condition. Malalignment, Malocclusion, Malposition and Malrelation are common terms used in describing unfavorable tooth positions. 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. Malar Relating to the cheek or cheekbone. See Zygoma. Mandible The lower jaw. Mandibular Resection (Osteotomy) Surgical removal of a part of the mandible to allow repositioning of the remaining parts. Mandibular Osteotomy Surgical sectioning of the mandible into two or more parts to allow repositioning of the resulting components. Masseter Muscle One of the powerful closing muscles of the lower jaw. (See pterygomasseteric sling). Often involved in so-called TMJ dysfunction complaints because of excessive nocturnal parafunctional activity. Materia alba White accumulation or aggregation of microorganisms, desquamated epithelial cells, blood cells and food debris loosely adhered to surfaces of teeth, soft tissues, dental restorations and orthodontic appliances. Less adherent than plaque, but may change into plaque. Maxilla One of a pair of 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 Of or pertaining to the upper jaw. May be used to describe teeth, dental restorations, orthodontic appliances or facial structures. Maxillary osteotomy Surgical sectioning and repositioning of maxillary bone structure to alter bone and jaw relationships. Maximum force An orthodontic force having the greatest magnitude within a range of force values that will produce tooth movement at a clinically acceptable rate. Mechanical action Force exerted on (received by) the body that is under study (for'determination of displacement and/or deformation of the body). Mechanical moment (of a concentrated force) The measure of the rotational potential of a force with respect to a specific line (axis) or point; in magnitude, the product of the size of the force and the distance (measured perpendicular to the line of the action) from the force to the moment axis or moment center. Mechanical reaction Force exerted by the body under study and upon the second body; two bodies are necessary to produce force, and forces always exist in pairs (identical to one another in magnitude and direction, but of opposite sense). Mechanical response Forces developed elsewhere in (or the displacement or deformation ofl a body (or assembly of bodies) as a result of force exerted at the activation-site' and constraints imposed on the body or bodies. Mechanical work A form of energy transfer characterized by forces acting through a distance. Mechanotherapy Orthodontic treatment by mechanical forces, acting on the dentofacial complex. Medial pterygoid muscle One of the powerful closing muscles of the lowerjaw. Part of the pterygomasseteric sling. Mediolateral The global direction perpendicular to a sagittal plane of the dentofacial complex; the medial direction/sense is toward, and the lateral direction/sense is away from the mid-sagittal plane. Megabyte (M) 1024 kilobytes (1,048,576 bytes) of information or storage space. Memory A computer's temporary data storage area (see RAM and/or ROM). Menton The most inferior point on the chin in the lateral view. A cephalometric landmark. Mesial Toward or facing the midline, following the dental arch. Used to describe surfaces of teeth as well as direction. Mesial Drift See Drift. Mesioclusion An occlusal relationship in which the lower teeth are positioned mesially, similar to the relationship in an Angle Class III malocclusion. Mesiodens A supernumerary tooth in the midline of the upper alveolar process. Often unerupted, it may inhibit or otherwise disrupt eruption and positioning of the incisor teeth. Mesiodistal The local direction tangent to the ideal arch form and parallel to the occlusal plane; the mesial direction/sense is toward, and the distal direction/sense is away from, the mid-line of the dentition. Midsagittal plane The imaginary, vertical plane that separates the left and right sides of the dentofacial complex. Mesocephalic Cranial form of average proportions (cephalic index between 76.0 and 80.9). Mesognathic Position of jaws forward from their normal position in relation to other facial structures. Microdontia Abnormal smallness of teeth, i.e. pegging in incisor region. Micrognathia An abnormally small jaw. Migration (dental) Spontaneous movement of a tooth or teeth after eruption. Milliroentgen (Mr) One thousandth of a roentgen; unit formerly used in measuring X-ray exposure. Millitad and millirem are currently used by radiologists. (See Rem) Mixed Dentition The developmental stage during which both deciduous and permanent teeth are present in the mouth (approximately 6 to 12 years of age). Model (dental) Popular name for a cast of a tooth or teeth, usually in plaster or similar material. Modem A device that can send and receive information from distant computers and information services over a phone line, send and receive Fax material, or simply dial telephone numbers. Moment A tendency to rotate resulting from the application of a force not through the center of resistance of a body. Moments are measured either as 1) the magnitude of a single applied force times the perpendicular distance the force acts away from the center of resistance, or 2) in the case of a couple, the magnitude of one of the forces of the couple times the distance between the forces of the couple. Monobloc A removable activator type orthodontic appliance. Mouthguard A removable elastic appliance used to protect the teeth and supporting tissues while engaging in contact sports. Movement First order movement Movement of teeth in a faciolingual or y direction; also known as in and out movements. Second order movement Movement of teeth in a mesiodistal, x, direction. Third order movement Movement of teeth in a vertical, z, direction. Monitor (CRT) A cathode ray video screen used to display data and graphics. The CRT must be matched to a display adaptor inside the computer. Mucosa The epithelial lining of body cavities opening to the outside. The oral mucosa lines all of the soft tissue surfaces of the mouth. Multi-tasking The ability to run several programs at one time on a terminal. Multi-user Several operators at terminals accessing the same files. Myalgia Muscle pain. Myofunctional Referring to the role of muscle function in relation to the teeth and jaws. - N - Natural head position A standardized orientation of the head, assumed when the subject focuses on a point in the distance at eye level. It is used for clinical examination of the face by anthropologists, orthodontists and maxillofacial surgeons. Neutroclusion Normal mesiodistal occlusal relationships of the buccal teeth. Nightguard (See mouthguard) A removable plastic appliance worn at night to prevent deleterious effects of nocturnal parafunctional activity (i.e. clenching, bruxism). Normal Deformation The deformation of a body accompanying the application to it of pulling or pushing force; tensile or compressive deformation perpendicular (normal) to a reference area of a body. Normal occlusion Optimal meeting of upper and lower teeth during function with no malocclusion present (such as rotations, malpositions or abnormal jaw relationships that are encountered in Class I, Class II and Class III malocclusion categories). - O - Obturator A prosthesis used to close an opening. Frequently used to close the defect caused by a cleft palate. 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). Occlusoapical The local direction perpendicular to the occlusal plane; also termed 'occlusogingival.' Occlusal dysfunction A term often used to describe abnormal functional forces and improper contact of upper and lower teeth. Untoward reaction beyond the teeth and investing tissues is claimed by some dentists, with the possibility of enhancing a multifactorial TMD etiology. Occlusal index A rating or categorizing system that assigns a numeric score or alphanumeric label to an individual's occlusion. There are five types: diagnostic, descriptive-epidemiological, treatment need or priority, treatment outcome, treatment complexity. 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 in the lateral view) based on specific reference points within the dental arches. Occlusion The relationship of the maxillary and mandibular teeth as they are brought into functional contact. Open bite A malocclusion in which some teeth cannot be brought into contact with opposing teeth. Open loop An auxiliary, fabricated of orthodontic wire, prepared such that the two 'legs' of the passive loop are nowhere in contact with one another. Opening loop An auxiliary fabricated of orthodontic wire that, upon mesiodistal-pulling activation, exhibits an enlargement of the plane area enclosed within its geometry. Oral Screen See screen. Orbitale The most inferior point on the lower border of the left orbit. A craniomettic and cephalometric landmark. Ortho- A prefix denoting straight or correct. Orthodontic (Orthopedic) Relating to correction of abnormal dental relationships, including facial structures and neuromuscular abnormalities. Orthodontic Attachment The element affixed to the tooth crown that transmits force from the arch wire or auxiliary to the dentition (e.g., a bracket). Orthodontic Displacement Tooth movement achieved through biomechanical remodeling of the periodontal ligament and/or the alveolar bone. Orthodontic force Force generated by the orthodontic appliance that contributes to the correlation of a malocclusion. Orthodontics/Dentofacial Orthopedics That area of dentistry concerned with the supervision, guidance and correction of the growing or mature dentofacial structures, including those conditions that require movement of teeth or correction of mairelationships and malformations of their related structures and the adjustment of relationships between and among teeth and facial bones by the application of forces and/or the stimulation and redirection of functional forces within the craniofacial complex. Major responsibilities of orthodontic practice include the diagnosis, prevention, interception and treatment of all forms of malocclusion of the teeth and associated alterations of their surrounding structures; the design, application and control of functional and corrective appliances; and the guidance of the dentition and its supporting structures to attain and maintain optimal occlusal relations in physiologic and esthetic harmony among facial and cranial structures. Orthodontist A dental specialist who has completed an ADA accredited advanced post-doctoral course of at least two academic years in the special area of orthodontics. Orthognathic Normal relationships of the jaws. 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 (orthopedic surgery) or by the application of appliances to stimulate changes in the bone structure by natural physiologic response (orthopedic therapy). Osseous Of or pertaining to bone. Ostectomy Surgical removal of a bone or part of a bone. Osteotomy Surgical procedure involving the cutting of bone. Output The information produced by a computer. Overbite Vertical overlapping of upper teeth over lower teeth, usually measured perpendicular to the occlusal plane. See overjet. Overjet Horizontal projection of upper teeth beyond the lower teeth, usually measured parallel to the occlusal plane. When not otherwise specified, the term is generally assumed to refer to central incisors and is measured from the labial surface of the lower tooth to the lingual surface of the upper at the level of the edge of the upper incisor. Unique conditions may sometimes require other measuring techniques. - P - 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. Hard Palate The anterior part of the palate that is supported by and includes the palatal extensions of the maxillary and palatine bones. Soft Palate The part of the palate lying posterior to the hard palate, composed only of soft tissues without underlying bony support. Velum posterior appendicular portion of soft palate. Palate-splitting appliance (RPE) Palatal Bar Maxillary lingual appliance, usually transpalatal, connected to the first molars and used to maintain width and increase anchorage. Palpation Digital manipulation and assessment of tissue on physical diagnosis. Panoramic Radiograph A radiographic tomograph of the jaws, taken with a specialized machine designed to present a panoramic view of the full circumferential length of thejaws on a singlefilm. Also know byseveral proprietary brand names of machines, most of which include 'pan' as a part of the name. (Also termed panoral or panorex.) Papilia (interdental) The gingival structures occupying the space between adjoining teeth. Parallel Interface A computer interface in which several bits of information (usually one byte) are transmitted simultaneously. Parallel Printer A printer that accepts information by way of a parallel interface. Pathname A full pathname includes the drive, root and any subdirectory names. Each name is separated by a backslash (\). For example, C:\WP51 refers to the WP51 Directory on the C Drive. C:\WP51\TEST refers to the TEST subdirectory (or file) on the WP51 directory, on the C Drive. Periapical Pertaining to the area and tissues around the apex (tip) of the root of a tooth. Periodontal Ligament The periodontal membrane, which serves a ligamentous function in tooth attachment. Periodontal Membrane (or Ligament) The fibrous tissue that occupies the space between tooth root and alveolar bone, providing a ligamentous physical attachment of the tooth to the bone and nourishment to the cementum surface of the root and the cells that permit tooth movement. Periodontal Pocket A periodontal disease condition characterized by an abnormally enlarged space between tooth and alveolar bone with destruction of the attaching periodontal membrane and invasion by oral epithelium. Often progressive, resulting in bone and tooth loss if not arrested by treatment. Periodontics That dental specially concerned with the maintenance of the health and integrity of the periodontal tissues that support the teeth. Periodontium The investing and supporting tissues of the teeth; the periodontal membrane and alveolar process. Pharynx That part of the respiratory tract extending from the larynx to the nasal cavity; the throat is a part of the pharynx. Physiologic force Force inherent in a biologic system (e.g., the pushing of blood against the vessel walls; the force working in the tooth eruption process; i.e. a light force. Pixel The elements of a radiograph. Each pixel of a digital image may be represented by one of up to 1024 shades of gray. A black and white television picture represents 256 shades of gray by way of comparison. 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. Pogonion The most anterior point on the chin. A cephalometric landmark in the lateral view. Point Size Points are the unit of measure normally used to measure font sizes. In Word Perfect, point equals 1/72nd of an inch. Point A The deepest point in the bony concavity in the midline below the anterior nasal spine, in the region of the incisor roots. Often called maxillary apical base. This is a landmark on the lateral cephalometric radiograph. Point B The deepest point in the profile curvature of the mandible, from Pogonion on the chin to infradentale Ounction of alveolar bone and the lower incisors) Also mandibular apical base. A landmark on the lateral cephalometric film. 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). Port A connection device between a computer and another component such as a printer or modem. For example, a printer cable is plugged into the printer port on the computer so information can be sent to the computer. Porter Arch A W-shaped palatal arch attached to the permanent first molars to expand one or both lateral segments of the maxillary arch. Wire loops can be incorporated in the anterior aspect of the palatal arch and in the two legs. (Quadrihelix arch) Positioner (tooth positioner) A removable elastic orthodontic appliance molded to fit the teeth on a 'setup' made by repositioning the teeth from a plaster cast. The material may be rubber or elastomeric plastic. It is typically used to achieve fine adjustments and retain corrected positions during the finishing stages of treatment. Posterior Nasal Spine The radiographic image on the lateral cephalogram that denotes the posterior terminus of the palatal plane. Postural Rest position The resting position of the mandible in normal posture. See freeway space, rest position. PPO (Preferred Provided Organization) A formal agreement between a purchaser of a dental benefits program and a defined group of dentists for the delivery of dental services to a specific patient population, as an adjunct to a traditional plan, using discounted fees for cost savings. Preangulared bracket An orthodontic bracket having its slot inclined to the ordinary mesiodistal direction, permitting the generation 6f second-order action from a passively straight wire. Pretorqued bracket An orthodontic bracket having its slot rotated with respect to the ordinary faciolingual direction, permitting the generation of third-order action from a passively straight (untwisted) rectangular wire of suitable cross-sectional dimensions. Preventive Orthodontic Treatment. Dental services intended to prevent the development of a malocclusion by maintaining the integrity of an otherwise normally developing dentition. Typical services include dental restorations, temporary prostheses (space maintainers) to replace prematurely lost deciduous teeth and removal of deciduous teeth that fail to shed normally when this will allow the permanent successors to erupt satisfactorily. Primary dentition (primary teeth) Teeth developed and erupted first in order of time. Deciduous teeth. Proclination Anterior coronal tipping of anterior teeth, as opposed to bodily protrusion, which indicates positional variation. Prognathic A forward relationship of the mandible or maxilla, relative to the craniofacial skeleton. Prognathism See Prognathic. Programmed Appliance placement Placing orthodontic attachments on the teeth successively over a period of time as dictated by treatment needs, as opposed to placement of all attachments at the beginning of treatment. Pronasale Most forward point of the tip of the nose. Proportionally-spaced fonts Proportionally-spaced fonts vary the amount of space given to characters in the font (e.g., the letter i usually gets less space than w). Prosthion The lowest and most forward point of the alveolar process between the maxillary central incisors. Protraction pertaining to desired anteriorly directed, orthodontic or orthopedic displacements of teeth or of bones of the face. Protrusion Teeth and jaws placed farther forward than normal. See also Prognathic, Mesognathic. Proximal segment That portion of a sectioned mandible containing the articulating portion. Pterygo-masseteric sling Term applied to combined internal pterygoid and masseter muscles on each side of mandible, as they join at lower posterior border of the mandible to provide combined activity to perform closing and masticatory functional movements. Pulp (dental) The soft tissue occupying the inner (pulp) chamber of a tooth. Consists of loose areolar tissue, blood vessels and nerves. Pure rotation A displacement of a body, produced by couple action, characterized by the center of rotation coinciding with the center of resistance. - Q - Quasi-static Descriptive of the configuration of the appliance and the dentition in an instantaneous or shortterm analysis between appointments: velocities, accelerations, and inertias are sufficiently small to be negligible such that the principles of static (mechanical equilibrium) may be used in the analysis. q.d. or q.i.d. Abbreviation of latin phrase `quater in die', i.e. 4 times a day. Used in prescription writing. quadrangular Having four angles. quadrant A fourth part. In dentistry, one half of each dental arch, the dividing line being the midpoint of the arch. There are thus four quadrants?the upper left and right and the lower left and right - R - R Point (Registration point) A cephalometric reference point introduced by Broadbent in his original presentation of the cephalometric technique. It is the midpoint on a perpendicular drawn from the center of sella turcica to the Bolton-nasion line. Rad A measurement unit of the absorbed dose of ionizing radiation; 1 R corresponds to an energy transferal of 100 ergs/gm. Also, see Rem. Milligad (mR) One one-thousandth of a rad. Normal background radiation in this country varies from about 50 to 200 mR per year, depending on geographic location. Radiation Energy propagated through space or matter in the form of waves, such as sound, light, radio, X-rays and cosmic rays. Also see X-ray. Radiograph A permanent image, typically on film. produced by ionizing radiation. Sometimes called an 'X-Ray' after the most common source of image-producing radiation. Radiographic imaging The process of acquiring representations of structures using ionizing radiation. RAM Random Access Memory is the working space or temporary storage area for the program you are using and the document on your screen. RAM is erased when the power is turned off. Ramus Paired vertical posterior parts of the mandible that serve as attachment areas for the muscles of mastication and also contain the condyles that articulate with the temporal bones. Plural; rami. Rapid palatal or maxillary expansron (RPE, RME) Orthopedic widening of the maxillary dental arch, usually with strong forces over a short period of time. Rare Earth screens Intensifying screens that are coated with special compounds to further reduce x-ray exposure for cephalometric and panoral films. Reciprocal forces Forces exerted by an orthodontic - or orthopedic - appliance component such that the component itself is subjected to just two non-negligible forces; the two delivered forces, then, are of the same magnitude and direction, but are opposite in sense to one another. Reference frame A set of two or three intersecting axes, ordinarily mutually perpendicular, used as a basis for locations of points and directions of lines, graphically expressing relationships among variables, or undertaking vector analysis, in a plane or in space. Rem (radiation equivalent-man) A unit of absorbed radiation dose adjusted for biologic effects equivalent to 1 rad of 25OKV X-rays (dental and cephalometric X-rays require less than 100KV). Millirem One one-thousandth of a rem. Replantation The replacement of a tooth that has been avulsed, usually as the result of an accident. Ankylosis is common in replanted teeth owing to injury to the periodontal membrane. Reproximation (slenderizing) Abrasive reduction of small amounts of enamel thickness on the proximal surfaces of the teeth, usually anteriors, to reduce overall width and space requirements (see interproximal stripping). Resection Surgical removal of part or all of a structure. Root resection Removal of the apical portion of the root of a tooth, usually to eliminate infection. Resilience The amount of energy transferred by mechanical work to take a body from an initial, passive state to its elastic limit; the area under the load-deformation plot up to the elastic limit. Resorption Physiologic or pathologic removal of hard tissue (bone or root) by the activity of osteoclasts. Syn; osteoclasis. Rest position The normal resting position of the mandible, with teeth apart and muscles relaxed. Retainer Any orthodontic appliance, fixed or removable, used to maintain the position of the teeth following corrective treatment. Retention The passive treatment period following active orthodontic correction during which retaining appliances may be used. Retraction Pertaining to desired posteriorly directed, orthodontic or orthopedic displacements of teeth or of bones of the face. Retroinclination Lingual (palatal) angulation (inclination) of anterior teeth. Retrognathic A mandible or maxilla that is retruded in its relationship with other facial structures, due to a size discrepancy or positional abnormality. Retrusion Teeth or jaws that are posterior to normal position or movement toward the distal. Reverse-pull or protraction headgear A (primarily) extraoral orthodontic or orthopedic appliance designed to deliver force to the dentition that is principally or totally anteriorly directed. Ribbon arch appliance An appliance developed by E.H. Angle prior to the Edgewise appliance, using a rectangular wire in a vertical slot to gain multidirectional control. Bracket was inverted and used by Dr. Begg for his technique. Rigid Fixation Stabilization of two bony segments, using metal plates or screws to eliminate movement between the parts. Roentgen A unit of radiation exposure to product in air 2.58 X 10-4 coulomb of ions per kilogram of air. Roentgenogram An image produced on film by roentgenography; radiograph is the preferred term. Roentgenography Production of permanent images through the use of Roentgen rays (x-rays). ROM Read Only Memory contains information the computer uses to run the system. ROM is permanent and is not erased when the power is turned off. 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). Root movement The transverse tooth movement characterized by little displacement of the crown and the center of rotation located on the long axis and at or near bracket level. Root Resorption Resorption of a part of the root of a tooth. Either internal (pulpal) or external surfaces may be affected, generally at the apex. Rotation Any orientation-changing whole-body displacement; a displacement characterized by the change in angulation of some line(s) in the body with respect to a specified reference frame. First order rotation Rotation of a tooth around the long axis; rotation in the x-y plane around the z axis. Second order rotation Rotation of a tooth in the x-z plane around the y axis. Also known as tipping. Third order rotation Rotation of a tooth in the y-z plane around the x axis. Also known as torquing. - S - Sagittal split A surgical procedure in which the rami of the mandible are split parallel with the sagittal plane, to allow repositioning of the mandibular body into a more favorable relationship with the maxilla. Screen (intensifying) See intensifying screen. Screen (Oral) A removable appliance, used to deflect or eliminate muscle forces on certain teeth. Commonly placed in the vestibule between the lips, cheeks and the teeth. Second-order clearance The angle through which an engaged arch wire may be tipped within the bracket slot, relative to the 'slot-parallel' configuration, before making contact with the occlusogingival slot surfaces. Second-order rotation A tooth as a whole rotates about a faciolingual axis. The angulation/orientation of the long axis of the tooth changes. Sella-Nasion(S-N) A frequently used cephalometric reference line connecting the center of the sella turcica with nasion. Sella Turcica (Sella; S) The pituitary fossa. The center is used as a cephalometric landmark. Separation An orthodontic procedure for slightly separating or spacing teeth, to seat bands or orthodontic attachments. Serial Extraction A program of selective or guided extraction of deciduous 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. Close supervision and control of ensuing eruption are essential, because overclosure of the spaces and other sequellae can be expected in a significant number of cases. Comprehensive orthodontic treatment is almost always required for space management, control of the tipping usually induced by the procedure and for other mairelationships that commonly accompany these conditions. Serial interface An interface in which information is transmitted one bit at a time. Serial printer A printer that accepts information from a computer by way of a serial interface. (Parallel printer communications are faster.) Setup A laboratory procedure in which teeth are removed from the plaster cast and repositioned in wax. May be used as a diagnostic tool to evaluate alternative treatment plans, particularly when orthognathic surgery is required in addition to orthodontic treatment. Shear deformation A change in shape as a result of loading (activation); often characteristically, a rectangular element assumes the form of a parallelogram. Sheath A synonym for a tube used as an orthodontic attachment. Shield See oral screen. Simple tipping The tooth movement produced by a labiolingually directed, concentrated crown force. Soft Palate The part of the palate extending posteriorly beyond the underlying bone; that which forms the division between mouth and upper pharynx. Sonic Digitizing. Digitization of surface landmarks using sound emissions received by an array or microphones. Differences in the time necessary for the sound to reach the various microphones are used by the computer to locate the digitized point in three planes of space. Space maintainer A prosthetic replacement for prematurely lost deciduous teeth intended to prevent closure of the space before eruption of the permanent successors. Often an urgent necessity in the buccal segment to prevent impaction of the permanent teeth and other complications. Space regainer Correction of tooth displacement resulting from premature loss of one or more deciduous teeth withouttimely space maintenance. Effective when the space loss is recent and small. May be accomplished with varying types of corrective appliances. Often most efficiently accomplished as a part of a comprehensive orthodontic treatment plan. Specialist 1. A person who devotes himself to diagnosis and treatment of one subject or to one particular branch of a subject or pursuit. 2. A health care practitioner who devotes his attention to a particular class of diseases, patients, etc. (Usually requires special training.) Spee, curve of The occlusal and incisal surfaces of the tooth crowns in either dental arch describe, from a sagittal perspective, a curve, ordinarily concave upwardwith referenceto the mandibulararch and convex for the maxillary arch. Splint A rigid appliance used to connect and mutually support teeth or bones. A removable form is often used to temporarily relieve occlusal interferences in functional disorders of the temporomandibular joint and related musculature. Split palate A removable or fixed palatal orthodontic appliance is divided in the sagittal plane, the two halves connected only by a jackscrew that is progressively opened to widen the palate and maxiffary dental arch. Spot grinding Equilibration of opposing tooth surfaces; also reshaping of teeth (i.e., removing mammelons, etc.). Spring-back The recovery exhibited by a beam, shaft, wire, or wire loop upon its unloading (deactivation) from a siate at or beyond its elastic limit. Stabilizing wire A stiff rectangular arch wirethat 'fills' the bracket slot and is used ordinarily to distribute a responsive force system throughout a dental segment. Stiffness The ratio of change in load to accompanying change in deformation of a member fabricated of a Hookean material and activated within its elastic limit; the slope of the load-versus-deformation plot beneath the elastic limit. Stomatognathic system Literally, the mouth-jaw system; the entire complex of structures of the head and neck involved in the functions of mastication, swallowing, respiration and speech. Stomion Intersection of the closed upper and lower lips. Stop A bend or auxiliary attachment placed on a wire to limit its sliding into a tube or in other orthodontic attachments. Straight wire A variation of the edgewise appliance in which brackets are angulated to minimize multiple archwire bends. Brackets and molar tubes have specific orientation in three planes' of space. Strain Local unit volumetric or distortional deformation experienced by a nonrigid body or structure subjected to external force. Strain energy Energy of a system characterized by constraints maintaining the system in a deformed configuration compared to a reference (passive) state. Stress (mechanical) Local intensity of distributed internal force experienced by a body or structure as a response to the application of external force to that body or structure. Stress-relief A heat-treatment process intended to reduce the magnitudes of residual ('locked-in') stresses induced by inelastic deformation. Stripping of teeth Term used for reproximating or slenderizing mesiodistal width of teeth, usually incisors. Subnasale The intersection of the columnella of the nose and the upper lip. Subspinale (Downs Point A) The most posterior point in the concavity between the anterior nasal spine and Prosthion. 'i.e. apical base.' Subtraction Radiography A darkroom technique in radiology which makes important radiographic information easier to see because it subtracts less important information from the image. Succedaneous Teeth Those permanent teeth that replace (succeed) the deciduous teeth, which include all permanent teeth except the permanent molars. Superelastic Refers to a metallic alloy having a relatively substantial elastic range; within a specific range of temperatures, the elastic portion of the force-deformation relationship for the alloy has two distinct, sequential parts because of a (submicroscopic) metallurgic phase-change that occurs as the force-magnitude is increased; a reversal of the phase-change occurs as the magnitude of force is subsequently decreased toward the passive state. Superoinferior The global direction perpendicular to the transverse plane of the dentofacial complex or the occlusal plane of one dental arch; the superior direction/sense is upward, and the inferior direction/sense is downward. Supernumerary Teeth Teeth in excess of the normal number. Often malformed or erupting abnormally. Supramentale (Downs Point B) The deepest point on the profile curvature from Pogonion to infradentale (i.e., apical base). Supraocclusion Overeruption of a tooth or teeth beyond the normal level, often as a result of tooth-loss or irregularity in the opposing arch. Surgical Fixation Stabilization of two bony segments for purposes of improving healing. Suture A fibrous junction between bones, as in the face and skull. Symphysis (mental) The union in the median plane of the two halves of the mandible. Syndrome A group of symptoms and/or deformities that occur together in a recognizable pattern, defining a specific disease or condition. Syntax The way certain elements are organized in an operation or set of computer instructions to make them function properly. - T - Technique (appliance) A method or procedure based on the use of certain appliances in specific ways. The variations and combinations are endless. Telescoping bite Total lingual crossbite of the lower arch. Temporomandibular articulation The bony articulation between the mandible and the temporal bones, consisting of the right and left temporomandibular joints. TMD Temporomandibular dysfunction. Temporomandibular joint (TMJ) One of the two paired articulations between the temporal bones of the skull and the mandible; the condylar process of the mandible articulates on the eminence of the glenoid fossa of the temporal bone. Tension Pertaining to the internal force and deformation experienced by a nonrigid body subjected to external force that tends to increase the characteristic length of that body. Therapeutic Diagnosis An assessment of the objectives and available methods of treatment in the light of conditions existing in the individual patient. Thermal Energy Energy possessed by a body because its temperature is higher than its surroundings. Third-order rotation A tooth as a whole rotates about a mesiodistal axis. The angulation/orientation of the long axis of the tooth is changed. Third-order clearance The angle through which an engaged rectangular arch wire may be rotated about its longitudinal axis, relative to the 'aligned-surfaces' configuration, before the edges of the wire make diagonal contacts with the occlusogingival slot surfaces. Third-order mechanical couple A couple, located in a mesiodistal plane, transmitted by a rectangular arch wire or torquing spur to an orthodontic bracket. Threshold force The minimum magnitude of force needed to produce a desired orthodontic displacement. Thumb (or finger) sucking A normal infantile activity sometimes extending into middle or late childhood. In certain situations, may produce or aggravate malocclusion. Tie Term used for fastening of ligature to brackets or archwires. Tie-back An omega loop, soldered or welded hook on an archwire, usually anterior to the molar tubes to fixate archwires in place. Tinnitus Noise in the ears such as buzzing, ringing, roaring, clicking; a symptom often reported in TMJ dysfunction problems. Tipping Tooth movement characterized by a change in angulation of its long axis without control of displacements of particles of the root(s). TMJ See temporomandibular joint. Toggle A feature or key that is turned on and off with the same keystroke. Tomograph A radiograph of a selected layer of the body produced while shifting the film and x-ray source in opposite directions around an axis located in the region of interest. This movement blurs outside structures while maintaining sharpness in the region of interest. Tongue Crib An appliance used to control undesirable and potentially deforming tongue movements. i.e., thrusting between the anterior teeth. Tongue Thrust Interposition of the tongue between the anterior teeth, especially in the initial stage of swallowing. This action, often combined with a resting position also between the teeth, can inhibit normal eruption and so produce an open bite. Tooth positioner See positioner. Tooth size discrepancy Lack of proportional harmony in the width (mesiodistal diameter) of various tooth crowns and the available space in the dental arch, causing relative spacing or crowding in different parts of the dentition. Torque An internal force system, carried longitudinally through a shaft or wire, and its resultant at any location is a mechanical couple in the plane of the right cross-section. Torque (dental) Tooth movement characterized by appliance-controlled faciolingual and/or mesiodistal displacements of particles in the root(s). Torque (mechanical) A force system, the simplest form of which is a mechanical couple, that tends to produce a twisting displacement and/or deformation about a long-dimension axis of the body acted upon; e.g., torque is delivered through crown attachments to teeth by an elastically twisted arch wire. Torquing displacement The rotational movement of a tooth resulting from the existence of an active second-and/or-third order action to the dentition. Torsional mechanical couple An active or responsive external couple exerted on a shaft or wire and directly associated with the turning and/or twisting of the member about its longitudinal axis. Torsiversion A tooth malposition characterized by rotation around the long axis of the root (not related to torque as described above). Torus A bulging bony prominence often found adjoining the palatal midline or low on the lingual alveolar surface of the mandible in the canine-premolar area. Toughness The maximum amount of energy, referenced to a passive state, transferred to a body in the form of mechanical work, that the body can absorb prior to structural failure (ordinarily by fracture or rupture); the total area under the load-deformation plot. Tracing (cephalometric) An overlay drawing traced from a cephalometric radiograph, showing specific structures and landmarks that may provide a basis for a variety of measurements. Traction Pertaining to a force-delivering component of an appliance that is mechanically activated by elastically extending its characteristic length; e.g., as in the stretching of an elastic module or a coiled spring. Transitional Dentition The final phase of the transition from deciduous to permanent teeth, in which the deciduous molars and canines are in the process of shedding and the permanent successors are emerging. Translation The movement of a body as whole such that the displacements of all particles of that body are alike (equal) in magnitude, direction, and sense. The angulation of the long axis remaining unchanged is necessary for a tooth movement to be translational. Any movement of a body that is not a translation in a rotation. Transposition Teeth positioned out of their normal position in the dental arch. (Teeth which have switched positions) Transseptal Fibers Gingival fibers traversing the septum between teeth, providing a fibrous connection between the teeth. Transverse displacement An orthodontic tooth movement characterized by displacements of points of the tooth at right angles (perpendicular) to the long-axis orientation. Transverse rotation A nontranslational tooth movement characterized by the axis of rotation positioned perpendicular to the long axis of the tooth. Trauma Tissue damage caused by an external force, such as a blow in an accident or abnormal clenching or grinding of the teeth. Trismus Muscle spasm (cramp). TSR A Terminate and Stay Resident Computer program. TSRs usually are loaded into memory before other programs and can be activated while running another program by using Hot Key combinations. Tuberosity The posterior aspect of the maxillary alveolar process. Turnkey Refers to a complete hardware/software package which is preloaded and ready to run when plugged in. Tweed Triangle A constructed triangle on the lateral cephalogram or tracing, formed by the mandibular plane, Frankfurt plane and the long axis of the mandibular incisor. Used as a diagnostic aid by C.H. Tweed. - U - Ugly Duckling Stage A stage of dental development during the incisor transition, characterized generally by linguoversion of mandibular lateral incisors, maialignment and flaring of maxillary lateral incisors, and a median diastema between the maxillary central incisors. These aberrations may be self-corrective, but could persistand require treatment. First recognized by B.H. Broadbent. Underbite An ambiguous non-technical term variously used to describe both retrusion and protrusion of the lower jaw. (archaic) Undermining Resorption A microscopic local condition in which resorption may occur beyond the active area, undermining bone spicules and so leading to their more rapid removal. 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. Uprighting Tipping inclined teeth to a more normal vertical axial inclination. Utility Arch Similar to a step-down or by-pass arch, used in the Ribbon Arch and edgewise technique to upright molars and depress anterior teeth. Ultrasonic (ultrasound) Having sound wave frequencies higher than those normally audible to the ear. Ultrasonic waves are used in medicine as a diagnostic tool to examine inter– nal organs. U. scaler. Scaling instru– ment with interchangeable tips of several shapes. The tips vibrate at ultrasonic speeds under a water spray. Should not be used on patients with a heart pacemaker. ultrasound See ultrasonic. ultra?violet light ray Radiation having wave length beyond that of the visible spectrum. Occurs naturally in sunlight or may be produced synthetically and used in sunlight treatment or to polymerize and harden certain fissure sealants or composite filling materials. unconscious Insensible. State in which there is a lack of appreciation of sensory impulses reaching the cerebrum. Undercut 1. Design feature of a tooth preparation achieved by cutting away tooth substance from below, or occurring by chance. It prevents the displacement of a restoration when set. 2. An overhung area of a tooth beneath which a clasp or band may be placed for retention of a prosthesis as may be indicated by a survey fine. U. ridge. Alveolar ridge in an edentulous mouth that has resorbed leaving an undercut below its crest thus making denture construction and insertion difficult. under?exposure Incomplete exposure time to X?rays of a radiographic film. undulate To move up and down. To cause to vibrate. unerupted Not yet erupted into the mouth. uni? Prefix meaning one. - V - V-Bends Place to mark, solder or twist wire. Velopharyngeal insufficiency. Anatomic or functional deficiency in the soft palate or superior pharyngeal constrictor muscle affecting closure of the opening between mouth and nose in speech, resulting in a 'nasal' speech quality. Version A suffix denoting tooth displacement; i.e., mesioversion transiatory displacement towards the mesial, axiversion (tipping) or torsiversion (rotation). Often, either transiatory displacements or tipping are labeled as mesloversion, distoversion. Vertex (anatomy) The most superior point on the top of the skull. Vertical Dimension The vertical relationship of the mandible to the maxilla in the rest or occluded position. Vertical elastic traction Pertaining to forces occlusally directed and delivered through orthodontic attachments to tooth crowns as the result of the (stretching) activation of an 'up-and-down' elastic band. Visceral Swallowing The term used to describe the swallowing pattern in which the tongue is thrust between the teeth. Visual Treatment Objective (VTO) A diagnostic and communication aid consisting of a cephalometric tracing or computerized projection, modified to show anticipated changes in the course of treatment. vaccinate To inoculate with a vaccine in order to produce immunity from a specific disease. Vaccination Introduction of a vaccine into the body by inoculation, to control or prevent infectious diseases by inducing an active immunity. The vaccine is placed upon the skin which is then scratched by a sterile needle or sharp surface. Also known as inocula–tion or immunization. vaccine Substance used in the prevention or treatment of various types of bacterial and virus infection. It may consist of (1) living but weakened pathogenic bacteria, e.g. BCG; (2) dead pathogenic bacteria, e.g. TABC; (3) modified bacterial toxins known as toxoids; or (4) living organisms of low virulence related to the disease itself. vacuole 1. Small cavity in the protoplasm of a cell. 2. Small space in tissue. vacuum Enclosed space from which air has been removed. V. fired porcelain. See porcelain. V. investing. Investment of a waxy pattern under vacuum conditions to reduce the possibility of small air bubbles being incorporated in the investment material itself. vagus nerve Tenth cranial nerve, having the most extensive distribution of all the cranial nerves, including the abdomen, chest, neck and head. VaGum? See diazepam. vallate Having a rim, as in the vallate papilla of the tongue. valve Fold in a canal or vessel that prevents the return of its contents. valvular Relating to a valve or valves. vaporize To change into a vapour by heating. vaporizer Apparatus enabling a liquid to produce a vapour for inhalation. Vapour Gaseous state of a substance that is liquid or solid at ordinary temperatures but emits a vapour on heating, e.g. mercury. varicella See chicken pox. variola See smallpox. varnish Solution of resin, shellac, copal, sandrac and other medicaments in a volatile solvent such as ether or alcohol. On evaporation it forms a thin protective adherent coating or film that may be a barrier against the deleterious effects of moisture or irritant substances. - W - W-Arch W-shaped maxillary expansion arch, usually soldered to the lingual of the maxillary molars. (Also known as Porter arch) Working Side The lateral segment of the dentition toward which the mandible is moved during masticatory function. Working wire An orthodontic arch wire, often rectangular, used to exert crown force systems capable of controlling or imparting root torque and the associated displacements in all three planes of space. Ward's wax carver See carver. warfarin Anticoagulant used in the treatment of thrombosis. Patients taking this drug or other anticoagulants may be liable to excessive bleeding after extractions. Trade name Marevan?. watch spring scaler See scaler. water Colourless, clear liquid, essential for life and found in all orga–nic tissues. Distilled w. Purified water obtained by distillation. W. coolant. Water spray directed onto a tooth surface being cut by a high?speed cutting instrument, in order to reduce and prevent pulpal damage caused by fric–tion heat. W. pik. Machine producing a water?jet spray for patient use in oral hygiene maintenance. wax Pliable substance obtained from plants and insects or synthetical–ly produced. Has many dental ap–plications. Bite w. Bite registration material, usually in the form of thin sheets, used to register the occlusion of upper and lower teeth. Bone w. Wax used for filling sterile bone cavities. Candelilla w. Naturally occurring wax used to harden inlay casting wax obtained from the candelilla shrub. Carnauba w. Naturally occurring wax obtained from the Brazilian wax palm and used to harden inlay casting wax. Carving w. Coloured, high?melting point wax, used chiefly for instruction in tooth carving exercises. Casting w. (inlay w.) Mixture of waxes such as paraffin wax, beeswax, ceresin wax, carnauba wax and candelilla wax. Used for pattern making for metallic castings, such as inlays, and designed to leave no residue when burned out of investment materials. The working temperature, hardness, suppleness, expansion and contraction of casting wax are controlled by the ingredients. Blue or green in colour and obtainable in sticks, thin sheets and prefabricated shapes for clasps and bars. Inlay wax. See casting w. Modelling w. Blend of waxes, usually pink, orange or red in colour, that is pliable at room temperature. The softening temperature range varies according to its intended use. I Paraffin w. Wax derived from crude oil and used as the major constituent in many dental waxes. Sticky w. Blend of waxes in the form of yellow sticks which, when heated, melt and adhere to the surface to which they are applied. Used primarily to hold components together before they are joined permanently. Wafer w. Thin strip of wax, in which a thin metal foil is sometimes embedded, used to make interocclusal records. W. knife.Metal instrument used to melt, carve and convey molten wax during the con–struction of dentures. It has a pointed flat blade at one end and a hollowed blade at the other, separated by a wooden or plastic handle. W. pattern Accurate pattern of a crown or inlay preparation made in blue or green inlay wax and used in the lost wax process during the casting of gold and other casting metals. waxing up Use of wax by the dental technician in making trial dentures. - X - X-bite Abbreviation for crossbite. X-ray Electromagnetic radiation produced when electrons strike a target under high voltage in a vacuum. X-ray, sometimes used incorrectly as a synonym for radiograph. xantho? Prefix denoting yellow. XCP See extension?cone paralleling technique. xeno? Prefix denoting foreign, alien or different. xenogenic graft See graft, xeno?. xero? Prefix denoting dry. xeroradiography Dry processing technique that produces paper prints of X?ray images by means of a selenium plate which records an image through the radiation?induced discharge of a positive electrostatic potential. xerostomia Dryness of the mouth due to lack of saliva. May be due to lack of proper function of the salivary glands, blockage of the salivary ducts or the action of drugs. X?ray digitizer Electromechanical system used to obtain direct readings of coordinates on an X?ray film for computer analysis. X?rays Part of the electromagnetic spectrum of radiation, having a shorter wavelength than light and more energy. When fast?moving electrons are decelerated by a solid object they produce X?rays with enough energy to produce an image on a film once they have passed though teeth, bone and soft tissue. Denser tissues stop more X?rays from passing through them than do ~ softer tissues, hence various shades of blackness appear on the film. Metal fillings appear white, teeth less white, and air spaces quite dark. X?ray tracing table Illuminated table used when tracing cephalometric radiographs. Xylocaine? See lignocaine. - Y - Yielding A substantial increase in strain with little or no increase in stress, occurring just above the elastic limit in some metallic materials. yawn Involuntary reflex action in which the mouth is opened wide and air drawn into the lungs. yaws Tropical disease resembling syphilis and which produces raspberry?like skin lesions on the face, palms of the hands and the soles of the feet. Y axis (of growth) Line joining the ?????Ila to the gnathion. yeast Microscopic, colourless, single?celled plants of the fungus group. As distinct from bacteria, they reproduce by the process of budding. - Z - zero 1. Nought, nothing, nil, the figure 0. 2. Point marked zero on a graduated scale. 3. Temperature corresponding to zero. zinc Hard bluish metal used in alloys such as brass in some dental amalgams and in galvanizing iron. Several of its salts are used in dentistry. Zinc poisoning may lead to a bluish grey pigmentation of the gingiva after a prolonged period. zinc acetate (or diacetate) Used in small quantities to accelerate the setting of zinc oxides and eugenol cements. zinc chloride Astringent, antiseptic, styptic, caustic and obtundent substance in the form of semitransparent sticks that are kept in a stoppered dark glass bottle. They gradually coalesce to form a caustic liquid and should not be handled. Used as an astringent on cotton wool or suing to control bleeding from gums and as a retraction agent. May be used as a 40 50% solution in water and applied for 1 minute to desensitize a sensitive tooth area. Zinc chloride has been incorporated into toothpaste as a desensitizing agent. It may also be used diluted as a mouthwash held in the mouth for 1 minute and used three times daily. Continued use changes the composition of the saliva. zinc free amalgam alloy See alloy. zinc oxide White, amorphous, odourless and tasteless powder with mild astringent properties usually mixed with other medicaments to form creams, powders or pastes. In dentistry, widely used as a solid component in filling materials, impression materials, periodontal packs and in some polishing agents. zinc oaide/EBA cement See EBA cement. zinc oxide eugenol cement Cement formed by mixing zinc oxide and eugenol the principal constituent of oil of cloves. Modifiers may be added to speed up the setting reaction. Used as an obtundent, antiseptic temporary dressing in a cavity, or as a means of temporarily cementing crowns, bridges and splints into place. May also be used as a root canal filling material. zinc oxide eugenol impression paste See impression material. zinc phosphate/oxyphosphate cement Hard cement made of a mixture of powder containing deactivated zinc oxide and colouring matter and of a solution of orthophosphoric acid in water. It should not be used too thin as its acidity may damage the tooth pulp. May be slaked to provide a longer working time. The synonym zinc oxyphosphate cement is deprecated. zinc polyacrylate cement See zinc polycarboxylate cement. zinc polycarboxylate cement (zinc polyacrylate cement) Deactivated zinc oxide powder mixed with a viscous 40% aqueous solution of polyacrylic acid to provide a non irritant, adhesive cement. It should not be used after the cobweb stage has been reached. zirconium oxide Finely ground powder used as a polishing agent in dentifrices. zoster An encircling pattern as in herpes (shingles). Z plasty Scar incision in the form of the letter Z. The two so formed triangles eliminate tension along the scar when sutured. Zsigmondy charting system Charting system widely used in the United Kingdom National Health Service. Employs numerals to identify permanent teeth and alphabetical letters A E for the deciduous teeth. See Appendix 3. 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. zygomatic arch Arch of bone arising from the zygoma and passing backwards to rejoin the skull just in front of the external opening to the ear. It serves to protect the eye.