ABO ABO Growth and Development 2 — Questions and Answers
Question 1: The Demirjian method for dental age assessment is based on which criterion?
- Root apex closure stages
- Seven lower-left permanent tooth calcification stages on panoramic radiograph (Correct answer)
- Eruption chronology of all 28 permanent teeth
- Bone age from the hand-wrist radiograph
Correct answer: Seven lower-left permanent tooth calcification stages on panoramic radiograph
The Demirjian method scores the calcification stage (A–H) of seven lower-left permanent teeth on a panoramic radiograph to estimate dental age.
Question 2: Skeletal age assessment using hand-wrist radiographs identifies peak pubertal growth using which landmark?
- Epiphyseal fusion of the distal radius
- Appearance and fusion of the sesamoid bone of the thumb (adductor pollicis) (Correct answer)
- Length of the middle phalanx
- Carpal bone count
Correct answer: Appearance and fusion of the sesamoid bone of the thumb (adductor pollicis)
The sesamoid bone of the thumb appears shortly before peak height velocity, making it a useful landmark for timing orthopedic interventions.
Question 3: In a patient with a Class II skeletal pattern, late mandibular growth is generally considered:
- Unfavorable, as it worsens the Class II discrepancy
- Favorable, as mandibular growth tends to reduce the ANB angle (Correct answer)
- Irrelevant to the final orthodontic outcome
- Always corrective regardless of direction
Correct answer: Favorable, as mandibular growth tends to reduce the ANB angle
Continued forward mandibular growth in a Class II patient tends to reduce the ANB angle and improve the skeletal relationship, which is favorable for long-term orthodontic stability.
Question 4: The Bolton ratio analysis compares which measurements to evaluate tooth-size discrepancy?
- Mesiodistal widths of upper vs. lower individual teeth at the canine only
- Sum of mesiodistal widths of all 12 lower anterior teeth vs. all 12 upper anterior teeth (overall ratio) or 6 vs. 6 (anterior ratio) (Correct answer)
- Arch perimeter of upper vs. lower arch
- Crown height of upper vs. lower anterior teeth
Correct answer: Sum of mesiodistal widths of all 12 lower anterior teeth vs. all 12 upper anterior teeth (overall ratio) or 6 vs. 6 (anterior ratio)
The Bolton analysis uses the ratio of the sum of mesiodistal widths of the lower 12 teeth to upper 12 teeth (overall) and lower 6 to upper 6 (anterior) to detect tooth-size discrepancies.
Question 5: Timing orthodontic Class III camouflage treatment in a growing patient is challenging because:
- Class III patients grow earlier than normal
- Continued mandibular growth may worsen the skeletal discrepancy after dental compensation is complete (Correct answer)
- Class III patients rarely respond to orthodontic forces
- Extraoral appliances are ineffective in Class III patients
Correct answer: Continued mandibular growth may worsen the skeletal discrepancy after dental compensation is complete
Dental compensations achieved during orthodontic treatment can be undone if the underlying skeletal Class III pattern continues to progress with late growth.
Question 6: The ANB angle represents the relationship between which anatomical landmarks?
- Articulare, Nasion, B-point
- A-point, Nasion, B-point (Correct answer)
- Anterior nasal spine, Nasion, Basion
- Articulare, N-perp, B-point
Correct answer: A-point, Nasion, B-point
ANB is the angle at Nasion formed by lines from A-point (subspinale) and B-point (supramentale), quantifying the sagittal jaw relationship.
ABO ABO Growth and Development 2
The Demirjian method for dental age assessment is based on which criterion?