ABO Orthodontic Diagnosis and Treatment Planning 2 — Questions and Answers
Question 1: A patient presents with a mandible positioned posteriorly and a convex profile. Which skeletal classification does this most likely represent?
- Skeletal Class I
- Skeletal Class II (Correct answer)
- Skeletal Class III
- Vertical maxillary excess
Correct answer: Skeletal Class II
A retrognathic mandible with a convex profile is characteristic of a skeletal Class II relationship.
Question 2: On a lateral cephalogram, the ANB angle measures 7 degrees. What does this indicate?
- Skeletal Class I
- Skeletal Class II tendency (Correct answer)
- Skeletal Class III tendency
- Ideal bimaxillary balance
Correct answer: Skeletal Class II tendency
An ANB angle greater than about 4 degrees suggests a skeletal Class II discrepancy.
Question 3: Which radiograph is most appropriate for evaluating impacted canine position in three dimensions?
- Panoramic film
- Lateral cephalogram
- Cone-beam CT (CBCT) (Correct answer)
- Bitewing radiograph
Correct answer: Cone-beam CT (CBCT)
CBCT provides three-dimensional localization of impacted teeth and adjacent root resorption.
Question 4: The Bolton analysis is used primarily to assess what?
- Tooth size discrepancy between arches (Correct answer)
- Skeletal growth direction
- Airway volume
- Condylar position
Correct answer: Tooth size discrepancy between arches
Bolton analysis compares the mesiodistal tooth-size ratio of maxillary to mandibular teeth to detect discrepancies.
Question 5: A negative value on space analysis in the mandibular arch indicates:
- Excess spacing
- Arch length deficiency (crowding) (Correct answer)
- Ideal alignment
- Overjet increase
Correct answer: Arch length deficiency (crowding)
A negative discrepancy means available arch length is less than required, indicating crowding.
Question 6: Which cephalometric measurement best evaluates the vertical growth pattern?
- SNA angle
- Mandibular plane angle (FMA) (Correct answer)
- Interincisal angle
- Wits appraisal
Correct answer: Mandibular plane angle (FMA)
The mandibular plane angle reflects the vertical facial growth pattern, with high angles indicating hyperdivergence.
Question 7: A patient with an anterior open bite and tongue thrust should first be evaluated for:
- Immediate extraction
- Underlying etiology such as habit or skeletal pattern (Correct answer)
- Fixed retention only
- Orthognathic surgery without records
Correct answer: Underlying etiology such as habit or skeletal pattern
Identifying the cause—habitual, skeletal, or functional—is essential before selecting open-bite treatment.
ABO Orthodontic Diagnosis and Treatment Planning 2
A patient presents with a mandible positioned posteriorly and a convex profile.
Which skeletal classification does this most likely represent?