ABO Orthodontics flashcards

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

SNA angle

Cephalometric angle from sella to nasion to point A, measuring anteroposterior maxillary position relative to the cranial base; adult norm is approximately 82 degrees.

SNB angle

Cephalometric angle from sella to nasion to point B, reflecting anteroposterior mandibular position; adult norm is approximately 80 degrees.

ANB angle

Difference between SNA and SNB, indicating the skeletal jaw relationship; a value of 2 degrees is normal, higher suggests Class II, lower suggests Class III.

Wits appraisal

Distance between the projections of points A and B onto the functional occlusal plane; positive values indicate maxillary prominence and negative values mandibular prominence, independent of cranial base.

Leeway space

Difference in combined mesiodistal width between primary molars and permanent premolars; approximately 1.5 mm per side mandibular and 0.9 mm per side maxillary.

Moyers mixed dentition analysis

Predicts combined widths of unerupted canine and premolars from the sum of the four mandibular incisors, using sex-specific percentile tables at 35th, 50th, and 75th percentiles.

Arch length discrepancy

Available arch perimeter minus the sum of required mesiodistal tooth widths; positive values indicate space excess, negative values indicate crowding requiring resolution.

Angle Class I

Molar relationship in which the mesiobuccal cusp of the maxillary first molar occludes in the buccal groove of the mandibular first molar.

Angle Class II

Molar relationship in which the mesiobuccal cusp of the maxillary first molar is mesial to the buccal groove of the mandibular first molar.

Angle Class III

Molar relationship in which the mesiobuccal cusp of the maxillary first molar is distal to the buccal groove of the mandibular first molar.

Cervical vertebral maturation

Staging of cervical vertebrae on lateral cephalograms (CS1-CS6) used to identify the pubertal growth spurt; CS3 and CS4 mark peak mandibular growth.

Maxillary protraction timing

Face mask protraction is most effective before approximately age 10, prior to fusion of circummaxillary sutures, for correction of maxillary deficiency.

Functional appliance window

Mandibular advancement appliances achieve greatest skeletal effect during the pubertal growth spurt, identified by cervical vertebral stages CS3 to CS4.

Optimal orthodontic force

Light continuous force producing tooth movement without ischemia; approximately 50-150 g per tooth for tipping and 100-200 g for bodily translation.

Anchorage ratio

Ratio of posterior to anterior resistance units; about 3:1 for maximum anchorage, 2:1 for moderate, and 1:1 for minimum anchorage.

Center of resistance

Point in a tooth or root where a single force produces pure translation; located approximately at the midpoint of the embedded root length.

Moment-to-force ratio

Ratio determining the type of tooth movement; low ratios produce tipping, intermediate ratios controlled tipping, and high ratios bodily movement or root torque.

External apical root resorption

Loss of root structure at the apex during orthodontic treatment; risk increases with heavy intrusive forces, prolonged treatment, and prior trauma.

Skeletal Class II treatment

Combination of growth modification (functional appliance or headgear), camouflage with extractions, or orthognathic surgery depending on severity and remaining growth.

Impacted canine management

Options include surgical exposure with orthodontic traction, extraction with substitution, or transplantation; choice depends on position, ankylosis, and arch space.

ABO OGS passing score

Objective Grading System scores eight criteria on a 0-2 scale; a cumulative total of 30 or better is required to pass the outcome assessment.

ABO OGS criteria

Eight scored parameters: alignment, marginal ridges, buccolingual inclination, occlusal relationships, occlusal contacts, overjet, interproximal contacts, and root angulation.

Discrepancy index

Pretreatment scoring system quantifying case complexity from crowding, spacing, overjet, overbite, cephalometric values, and missing teeth; higher scores indicate greater difficulty.

Cast Radiographic Evaluation

ABO requirement for a complete diagnostic record set including study casts, panoramic and cephalometric radiographs, periapical films, and clinical photographs.

Case report requirements

Submission must include problem list, diagnosis, treatment objectives, treatment plan with alternatives, mechanotherapy description, and comparison of pre- and post-treatment outcomes.

Board case categories

Submitted cases are distributed across Angle classification and treatment modality, including nonextraction, extraction, surgical, growth modification, and craniofacial categories.

Scenario-based oral exam

ABO examination format presenting clinical scenarios to assess differential diagnosis, risk assessment, informed consent, and management of complications or relapse.

Record quality standards

Diagnostic radiographs must show root apices and condyles; photographs must be standardized; casts must be trimmed in centric occlusion for valid assessment.

Informed consent elements

Discussion of diagnosis, treatment alternatives including no treatment, expected duration, risks such as root resorption and relapse, and responsibilities of patient and guardian.

Relapse risk factors

Incomplete correction, inadequate retention, persistent habits, third molar eruption, and failure to address transverse or torque discrepancies increase post-treatment relapse.

Retention protocol

Fixed lingual retainers and removable appliances maintain alignment; duration depends on initial discrepancy, age, and periodontal status, often indefinite for lower incisors.

Maintenance of certification

ABO diplomate status is time-limited; renewal requires periodic re-examination or documented continuing education to maintain active certification.

Iatrogenic effects recognition

Board scenarios assess identification of enamel decalcification, root resorption, gingival recession, and temporomandibular symptoms arising during orthodontic treatment.