ABO Orthodontics cheat sheet

Cephalometric norm anchors (adult white norms): SNA 82° ± 2°, SNB 80° ± 2°, ANB 2° ± 2°; ANB > 4° suggests skeletal Class II, ANB < 0° suggests skeletal Class III.

Wits appraisal measures the AO-BO distance projected onto the occlusal plane; positive values indicate the maxilla is ahead of the mandible and are independent of the S-N reference.

Leeway space is approximately 1.5 mm per side in the mandible and 0.9 mm per side in the maxilla; this E-space is available for molar correction during the mixed dentition.

Moyers prediction of combined mesiodistal widths of unerupted mandibular canine and premolars from the sum of the four mandibular incisors: at the 75th percentile, add 0.0 mm for females and 0.0 mm for males for a 21.0 mm incisor sum; always use the appropriate percentile table.

Arch length discrepancy = available arch perimeter minus required mesiodistal tooth width; a discrepancy greater than about 4 mm per arch usually requires extraction or distalization to resolve crowding.

Angle classification: Class I = mesiobuccal cusp of maxillary first molar in the buccal groove of the mandibular first molar; Class II = MB cusp mesial to the groove; Class III = MB cusp distal to the groove.

Growth modification timing: maxillary protraction is most effective before approximately age 10 (before midface sutural fusion); functional appliances for mandibular advancement are most effective during the pubertal growth spurt (CS3-CS4 on cervical vertebral staging).

Force levels: light continuous orthodontic forces of 50-150 g per tooth for tipping and 100-200 g for translation; intrusive forces should be lighter than extrusive forces to avoid root resorption and tissue necrosis.

Anchorage ratio (molar:anterior) for maximum anchorage is approximately 3:1 or greater; for moderate anchorage about 2:1; for minimum anchorage about 1:1.

ABO clinical examination components: a case-based written/clinical assessment plus a scenario-based oral examination; candidates must demonstrate diagnosis, treatment planning, and outcome assessment on submitted and/or unseen cases.

The ABO objective grading system (OGS) scores eight criteria-alignment, marginal ridges, buccolingual inclination, occlusal relationships, occlusal contacts, overjet, interproximal contacts, and root angulation-each on a 0-2 scale, with a passing total of 30 or better.

The Cast Radiographic Evaluation (CRE) requires a complete diagnostic record set: study casts, panoramic radiograph, cephalometric radiograph and tracing, intraoral/periapical radiographs, and clinical photographs.

Case report format requires a problem list, diagnosis, treatment objectives, treatment plan with alternatives, mechanotherapy description, and a final outcome assessment comparing pre- and post-treatment records.

Discrepancy index (DI) quantifies case complexity from pretreatment records (crowding, spacing, overjet, overbite, cephalometric values, missing teeth); higher DI values indicate more complex cases.

Board case categories are typically organized by Angle classification and treatment modality (nonextraction, extraction, surgical, growth modification, craniofacial anomaly); candidates must submit a balanced distribution.

Oral examination scenarios probe clinical judgment: differential diagnosis, risk assessment, informed consent, management of relapse, and recognition of iatrogenic effects.

Record quality standards require diagnostic-quality radiographs with visible root apices and condyles, standardized photographs (facial, intraoral), and casts trimmed in centric occlusion.

The ABO certification is time-limited; maintenance of certification requires periodic re-examination or continuing education to retain diplomate status.