OMSB Orthodontist (OEORDNT) key terms

A reproducible bony or soft-tissue point on a lateral or posteroanterior radiograph, such as Sella, Nasion, or Point A, used to construct planes and angles for skeletal and dental measurement.

A sagittal jaw relationship measure that projects the occlusal contact points of the upper and lower incisors onto the functional occlusal plane, avoiding reliance on cranial base reference points.

The angle formed between the A-point–Nasion line and the B-point–Nasion line, indicating whether the maxilla and mandible are in a Class I, II, or III sagittal relationship.

Categorization of the jaws as Class I, II, or III based on their relative sagittal position rather than on molar or canine occlusion alone, guiding whether treatment must address growth or surgery.

A tooth-size analysis comparing the summed mesiodistal widths of upper and lower teeth to detect anterior or overall arch length discrepancies that would prevent ideal interdigitation.

Calculation of the difference between available arch perimeter and the space required to align teeth, determining whether extraction, expansion, or interproximal reduction is needed.

The numerical mismatch between the space available in an arch and the space needed for the teeth, recorded as a positive value for crowding and a negative value for spacing.

Evaluation of hand-wrist radiographs or cervical vertebral shape to estimate remaining facial growth, helping time functional appliances, headgear, or growth-modifying treatment.

A staging method using changes in the shape of cervical vertebrae on a lateral cephalogram to estimate the pubertal growth spurt without an additional hand-wrist radiograph.

The period of accelerated skeletal growth around adolescence, peaking roughly two years earlier in girls than boys, which strongly influences the timing and effectiveness of orthopedic treatment.

Two mechanisms of bone change: remodeling alters bone surfaces without moving the whole bone, while displacement moves a bone as a unit, often accompanied by secondary surface remodeling.

The direction in which the mandible rotates during growth, described as forward (counterclockwise) or backward (clockwise), affecting chin projection, facial convexity, and open-bite tendency.

The point in a tooth or segment at which a single applied force produces pure translation without rotation; its location determines how a force system moves the tooth.

The point about which a tooth appears to rotate when a force system is applied; its position depends on the ratio of moment to force and defines tipping versus bodily movement.

The quotient of the applied moment divided by the applied force at the bracket, predicting whether a tooth will tip, translate bodily, or rotate around a controlled root point.

An appliance configuration in which the number of unknown reaction forces exceeds the available equilibrium equations, so tooth movement cannot be predicted from statics alone and must be observed clinically.

Resistance to unwanted tooth movement that provides the reaction force for moving target teeth; classified as maximum, moderate, or minimum depending on how much movement of the anchor unit is acceptable.

A small titanium screw or plate placed in bone to provide skeletal anchorage, allowing retraction or intrusion of teeth without reciprocal movement of the anchoring teeth.

Sliding of an archwire through brackets during space closure, where resistance from ligation, bracket angulation, and surface roughness reduces the effective force delivered to the teeth.

Use of bent archwire loops to close space, where the loop geometry and preactivation generate a defined moment-to-force system that can produce controlled translation of anterior teeth.

Retraction of the entire anterior segment as a unit along the arch, typically over a continuous archwire, rather than retracting individual teeth sequentially.

Management of the vertical position of incisors and molars during treatment to avoid bite opening or deepening, using intrusion, extrusion, or occlusal-plane mechanics as needed.

The anteroposterior curvature of the occlusal surfaces from the canine to the last molar; an exaggerated curve reduces available arch space and often requires leveling by incisor intrusion or molar extrusion.

A removable appliance that uses muscle forces and mandibular repositioning to alter dentofacial growth, commonly used in growing Class II patients to advance the mandible.

A two-piece removable functional appliance with upper and lower bite blocks whose inclined planes guide the mandible forward on closure, allowing wear during meals and combined fixed-appliance use.

An extraoral appliance that delivers force to the maxilla or maxillary teeth through a facebow and straps, used to restrict forward maxillary growth or to reinforce anchorage during retraction.

Orthopedic protraction of the maxilla using a forehead-chin support and elastic traction to the upper teeth or a splint, typically for growing patients with maxillary deficiency.

Separation of the midpalatal suture with a fixed expander turned at a prescribed daily rate, widening the maxilla and improving transverse deficiency and nasal airway dimensions.

A mismatch in width between the maxilla and mandible, often presenting as posterior crossbite or a narrow arch, assessed clinically and with posteroanterior or occlusal radiographs.

The combined clinical, cephalometric, photographic, and model evaluation used to plan jaw repositioning, including prediction tracing and coordination of orthodontic and surgical movements.

An intermediate occlusal wafer fabricated from model surgery or digital planning that positions the jaws in their planned relationship during fixation at the time of orthognathic surgery.

Physical or digital repositioning of mounted dental casts to simulate planned jaw movements, producing measurements and splints that guide the surgical procedure.

The phase after active treatment in which appliances or fixed retainers hold teeth in their corrected positions while periodontal and gingival fibers reorganize and relapse forces subside.

Return of teeth or jaws toward their pretreatment positions after treatment, driven by periodontal fiber tension, growth, soft-tissue pressures, or failure to remove the original cause.

A bonded wire, usually lingual to the anterior teeth, that maintains alignment long term; requires monitoring for bond failure, wire fracture, and accumulation of plaque.

The documented process of explaining diagnosis, treatment options, expected duration, risks, and alternatives so the patient or guardian can make a voluntary treatment decision.