Mixed Deck — All ABO Topics Flashcards

Root resorption during orthodontic treatment is most commonly detected using:

Answer: Periapical radiographs or CBCT

Periapical radiographs reveal root length changes due to resorption, and CBCT provides three-dimensional detail of root morphology and resorption extent.

Which of the following is a primary indication for extraction in orthodontic treatment planning?

Answer: Severe arch length deficiency with bimaxillary protrusion

Severe crowding combined with dental protrusion often requires extraction to relieve the discrepancy.

The cephalometric landmark Articulare (Ar) is located at the intersection of which anatomical structures?

Answer: Posterior border of the mandibular ramus and the inferior surface of the cranial base

Articulare is defined as the intersection of the posterior border of the mandibular ramus (or condylar neck) with the inferior border of the cranial base, used when the condyle is not well visualized.

Which record is essential for evaluating the transverse dimension and posterior crossbite?

Answer: Frontal (PA) cephalogram or study models

A posteroanterior cephalogram and study models assess transverse width and posterior crossbites.

Frictionless (loop) mechanics differ from sliding mechanics because they:

Answer: Use closing loops to deliver force without sliding along the wire

Loop mechanics activate bends/loops to move teeth without the tooth sliding along the archwire, avoiding friction.

Placing a reverse curve of Spee in the lower archwire is intended to:

Answer: Level the curve of Spee by extruding premolars and intruding incisors/molars

A reverse curve of Spee creates intrusive forces on the anteriors and molars while extruding the premolars to level a deep curve of Spee.

In the ABO Written Examination, which reference domain covers the biological basis of tooth movement including periodontal ligament response to force?

Answer: Biomechanics and biology

Tooth movement biology and periodontal ligament force response fall under the biomechanics and biology domain.

A patient with an anterior open bite and tongue thrust should first be evaluated for:

Answer: Underlying etiology such as habit or skeletal pattern

Identifying the cause—habitual, skeletal, or functional—is essential before selecting open-bite treatment.

The Andresen activator corrects Class II malocclusion by:

Answer: Advancing and posturing the mandible forward during sleep

The Andresen activator holds the mandible in a protruded position during sleep, directing condylar growth and restricting maxillary forward displacement.

The nasolabial angle is measured between which two lines?

Answer: The columella of the nose and the upper lip

The nasolabial angle is formed between the columella (bottom of the nose) and the upper lip, with a normal range of approximately 90–110 degrees.

A force applied at a distance from the center of resistance of a tooth produces which type of movement?

Answer: Tipping combined with rotation

A single force offset from the center of resistance creates a moment, causing tipping (rotation) plus translation.

Which bracket prescription is characterized by built-in torque, tip, and in-out values to reduce the need for wire bending?

Answer: Preadjusted edgewise bracket

The preadjusted edgewise (straight-wire) bracket incorporates built-in torque, tip, and in-out compensations to minimize wire adjustments.

What is the discrepancy index in ABO case assessment?

Answer: A scoring system measuring the complexity of a malocclusion based on multiple criteria including overjet, overbite, crowding, and skeletal pattern

The ABO Discrepancy Index quantifies malocclusion complexity by scoring criteria including overjet, overbite, anterior open bite, crowding, occlusal relationships, lingual posterior crossbite, and cephalometric measurements.

When using a bionator appliance, the mandible is typically advanced by how much from the rest position to create an orthopedic stimulus?

Answer: 2–4 mm

A 2–4 mm mandibular advancement is sufficient to stimulate condylar growth without exceeding the patient's neuromuscular adaptation capacity.

Which of the following is a normal finding in the early mixed dentition that does NOT require orthodontic intervention?

Answer: Mild crowding due to tooth-size/arch-size discrepancy that may self-correct

Mild crowding in the early mixed dentition can resolve naturally as the leeway space is utilized during the transition to permanent teeth.

Orthodontically forced eruption (extrusion) of a fractured tooth prior to crown placement serves to:

Answer: Bring the fracture margin supragingivally and develop bone/tissue for restorative margins

Forced eruption brings the fracture line coronal to the alveolar crest and gingival margin, providing adequate tooth structure and biological width for a crown.

The Herbst appliance corrects Class II malocclusion primarily through which mechanism?

Answer: Mandibular advancement and restraint of maxillary growth

The Herbst appliance postures the mandible forward continuously, stimulating mandibular growth and restraining maxillary forward development.

The term 'post-retention stability' in orthodontics refers to:

Answer: Long-term maintenance of corrected tooth positions after retainers are discontinued

Post-retention stability describes how well the corrected tooth positions are maintained after the patient ceases retainer use.

Nighttime-only retainer wear is typically appropriate beginning at which stage?

Answer: After approximately one year of full-time wear

After approximately one year of full-time retainer wear to allow periodontal reorganization, most patients can transition to nighttime-only wear.

What is a primary indication for early interceptive orthodontic treatment?

Answer: Developing malocclusions

A primary indication for early interceptive orthodontic treatment is the presence of developing malocclusions that, if left untreated, could worsen or become more complex. Examples include severe crowding, crossbites, or significant jaw discrepancies in children. Addressing these issues early can guide proper jaw growth, create space for permanent teeth, and simplify or even prevent the need for more extensive future treatment.