OMSB Orthodontist (OEORDNT) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

ANB angle

Cephalometric angle between A point, nasion, and B point; 2-4 degrees indicates skeletal Class I, greater than 4 degrees Class II, and less than 0 degrees Class III.

Wits appraisal

Projects A and B points onto the occlusal plane; the distance AO-BO assesses sagittal jaw relationship with less cranial base influence than ANB.

Bolton anterior ratio

Ratio of summed mandibular anterior tooth widths to maxillary anterior widths, normally about 77.2 percent; deviation signals tooth-size discrepancy affecting overjet and overbite.

Arch length discrepancy

Available arch perimeter minus required mesiodistal tooth width; positive values indicate spacing and negative values indicate crowding requiring treatment decisions.

Cervical vertebral maturation

Six-stage assessment of cervical vertebral shape on lateral cephalograms used to estimate skeletal maturity and timing of the pubertal growth spurt.

Leeway space

Difference in mesiodistal width between primary canine and molars versus permanent successors; about 1.5 mm per side mandibular and 0.9 mm maxillary.

Functional matrix theory

Moss's concept that soft tissue function and spaces drive skeletal growth, with bone responding to the demands of surrounding tissues rather than genetics alone.

Scammon growth curves

Four tissue growth patterns: neural grows early, lymphoid overshoots then involutes, genital grows late, and general somatic tissue follows an S-shaped curve.

Center of resistance

Point where a force produces pure translation; for single-rooted teeth it lies near one-third of root length apical to the alveolar crest.

Moment-to-force ratio

Ratio determining tooth movement type; low values cause tipping, intermediate controlled tipping, higher values translation, and highest values root torque.

Anchorage classification

Maximum, moderate, and minimum anchorage describe resistance to unwanted tooth movement; reciprocal movement occurs when anchorage units are equal in size.

Temporary anchorage device

Miniscrew or miniplate placed in bone to provide absolute anchorage for intrusion, retraction, or molar distalization without relying on teeth.

Adams clasp

Removable appliance retainer with arrowheads engaging mesial and distal undercuts of a tooth; provides strong retention with minimal coverage.

Twin Block appliance

Two-piece functional appliance with upper and lower bite blocks and interlocking inclined planes that posture the mandible forward during closure.

Facemask protraction

Extraoral appliance applying anteriorly directed force to the maxilla, used for Class III maxillary deficiency, most effective before late adolescence.

Rapid maxillary expansion

Skeletal expansion by opening the midpalatal suture with a fixed jackscrew appliance; most effective before sutural fusion in late adolescence.

Le Fort I osteotomy

Surgical separation of the maxilla at the Le Fort I level allowing advancement, impaction, setback, or segmentation for skeletal correction.

BSSO

Bilateral sagittal split osteotomy of the mandible; the most common orthognathic procedure, allowing advancement, setback, and rotation.

Presurgical decompensation

Orthodontic movement that removes dental compensation before surgery, exposing the true skeletal discrepancy so the surgical correction is accurate.

Distraction osteogenesis

Gradual surgical lengthening of bone by controlled separation of osteotomy segments; used for severe mandibular or maxillary hypoplasia in growing patients.

Genioplasty

Surgical repositioning of the chin by osteotomy, independent of occlusion; often combined with mandibular surgery to improve facial profile.

Virtual surgical planning

Use of CBCT and software to simulate osteotomies, plan movements, and fabricate guides or splints before orthognathic surgery.

Hawley retainer

Removable acrylic appliance with labial wire and Adams clasps; allows minor finishing adjustments and is durable for long-term retention.

Essix retainer

Vacuum-formed clear plastic overlay retainer; esthetic and effective for alignment but less durable and may increase occlusal coverage.

Fixed lingual retainer

Bonded wire on the lingual surface of anterior teeth; maintains alignment long term but requires monitoring for bond failure and oral hygiene.

Relapse causes

Periodontal fiber memory, soft tissue pressure, continuing growth, and unresolved original etiology can move teeth after appliance removal.

Informed consent

Documented discussion of diagnosis, treatment options, risks, expected duration, fees, and retention responsibilities before treatment begins.

Interceptive orthodontics

Early treatment of habits, crossbites, and space problems to reduce later complexity; examples include habit appliances and space maintainers.

Cephalometric tracing

Identification of skeletal and dental landmarks on a lateral cephalogram to measure angles and distances for diagnosis and treatment planning.

Scissors bite

Transverse discrepancy where maxillary posterior teeth are buccal to mandibular posteriors; may require expansion or surgical correction.

Herbst appliance

Fixed functional appliance with telescoping arms that hold the mandible forward; effective for Class II correction during the growth spurt.

High-pull headgear

Extraoral appliance applying force to the maxilla with a high pull vector, intruding and distalizing molars while limiting extrusion.