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.
flush terminal plane A developmental stage. The normal and desirable time-linked relationship of the distal surfaces of the maxillary and mandibular second primary molars.
flux A material used when soldering or brazing to remove surface oxides and impurities and to improve wetability.
FMA Cephalometric assessment of the inclination of the lower border of the mandible to the Frankfort plane.
FMIA Common cephalometric assessment of the mandibular incisor inclination with the lower border of the mandible.
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.
Fränkel appliance (introduced by Rolf Fränkel) An activator type functional appliance that is intended to stimulate or inhibit jaw growth, retrain muscles or widen the dental arches. It is unique in that it is the only tissue borne functional appliance.
free-way space The clearance or interocclusal distance between the maxillary and mandibular teeth when the mandible is in its postural resting position.
frenectomy The surgical removal or repositioning of a frenum. Performed to enhance the stability of a corrected diastema or to alleviate a “tongue-tie”.
frenum A fold of mucous membrane and underlying fibrous tissue that connect lip, cheek or tongue to the alveolar mucosa. (May be labial or lingual).
friction A resistance to the relative displacement of contacting bodies in a direction tangent to the plane of contact.
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. More correctly termed a posters-anterior (P-A) cephalometric radiograph. See cephalometric radiograph.
full treatment Comprehensive orthodontic treatment including both maxillary and mandibular dental arches.
functional appliance A term used to describe to a class of appliances which utilize the muscle action of the patient to produce orthodontic or orthopedic forces.
functional jaw orthopedics The form of therapy, usually with activator-type appliances, that utilizes the musculature to create dentofacial changes.
functional matrix A theory, which explains the interrelationship between osteogenesis and local functional demands, proposed by Melvin L. Moss.
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 -
gemination (twinning) Abnormal tooth development due to incomplete division of a single tooth bud.
genial Pertaining to the chin.
genioplasty A surgical procedure designed to reshape the contour of the chin, usually by augmentation or reduction.
gingivaThe fibrous investing tissue, covered with epithelium, which immediately surrounds the teeth and is contiguous with the periodontal ligament and with the mucosal tissues of the mouth.
gingival attachment The fibrous attachment of the gingiva to the tooth/teeth.
gingival crevicular fluid (GCF) The fluid that usually seeps into the sulcular area around the tooth from the crevicular epithelium. The flow of this fluid is increased in the presence of inflammation.
gingival display Measure of exposure of gingival tissue during a smile. See gummy smile.
gingival graft A surgical procedure usually performed to establish an adequate amount of attached gingiva around a tooth or group of teeth.
gingival recession Shift of a gingival margin apically so that part of the root of the tooth is exposed.
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).
glossectomy Partial or total resection of the tongue.
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.
golden proportion The ratio between succeeding terms in a mathematical progression (Fibonacci series) in which each number is the sum of the preceeding two numbers (1, 1, 2, 3, 5, 8, 13, 21, ……..). The ratio converges approximately on 1.618 to 1. It is suggested that such a ratio exists in the natural dentition, the balanced faces, skeletal structures and thus used in orthodontics.
gonial angle The most postero-inferior point on the angle of the mandible. It is located where the mandibular 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 or parafunctional activity.
group function Multiple simultaneous contacts of several maxillary and mandibular teeth on the working side in lateral movements of the jaw during which forces are distributed on a number of teeth.
growth 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 development and/or the effects of treatment.
growth potential An estimation of the amount of growth yet to occur.
growth site An area where growth occurs.
growth spurt An increase in the rate of growth (velocity) during adolescence. It usually occurs at 10-12 in the female and 12-14 in males coincident with the events of puberty.
guard, mouth See 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.
guided tissue regeneration (GTR) A procedure that attempts to regenerate lost periodontal tissues or alveolar bone through differential tissue response.
gummy smile A popular term for excessive exposure of maxillary gingival tissue during a full smile.
- H -
habitIn dentistry, a term applied to frequently repeated negative 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 with counseling or with 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 which can be used to evaluate the progress of the individual toward maturity (bone age or developmental age or skeletal age).
hardness The resistance of metal to plastic deformation by indentation. The most common method of measurement is Rockwell. Other methods are Brinell, Tukon and Vickers.
hardness number The number used to designate the hardness of metal. The number is related to the scale of values of a particular hardness test, as Rockwell B 80 or Brinell 150.
Hawley appliance A Hawley retainer modified to allow for minor corrective procedures.
Hawley retainer A passive removable acrylic and wire appliance, generally used to stabilize teeth in their new position after orthodontic correction. See retainer.
headcap The component of an (primarily) extraoral appliance that distributes and transfers responsive force to the cranium.
headfilm A common term for a cephalometric radiograph.
Health Maintenance Organization (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 healthcare services and may be required to remain in the program for a specified amount of time. See DHMO.
helix A spiral bend placed in an orthodontic archwire in the shape of a closed circle.
hemisection The procedure of sectioning a multirooted tooth, most commonly the mandibular molar.
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. It is named for Emil Herbst.
high angle malocclusion A general term applied to a craniofacial pattern in which growth is more vertical than normal; more specifically, a patient with an unfavorable steep 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 so 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. (also called transverse horizontal axis).
holding arch See lingual arch.
Hooke's law The ratio of mechanical stress to mechanical strain is a constant, as in an elastic modulus of material.
hypercementosis An excessive deposition of cementum.
hyperdivergent A facial pattern which includes a high angle of the mandible to Frankfurt plane, 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 due to 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 Congenital absence of one or more teeth.
hypoplasia Incomplete development of a tissue or structure.
hysteresis The lagging or delay in the effect of a system’s change. In orthodontics, the term is often used for the load deflection curve of the superelastic wires where there is separation between the loading and unloading curves.
- 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.
idiopathic Pain, disease or disorder of unknown causation.
imaging The process of acquiring representations of structures in either two or three dimensions.