ABO ABO Growth and Development

Question 1

The primary site of mandibular growth that contributes most to mandibular lengthening in adolescents is:

Accepted Answer

Condylar cartilage (endochondral growth at the condyle)

Answer

The condylar cartilage undergoes endochondral ossification, adding new bone to the posterior-superior condyle and lengthening the mandible.

Question 2

Normal primary (deciduous) dentition eruption begins with which tooth?

Accepted Answer

Lower central incisor

Answer

The mandibular central incisors are typically the first primary teeth to erupt, at approximately 6–10 months of age.

Question 3

The 'ugly duckling stage' of dental development is characterized by:

Accepted Answer

Spacing and flaring of upper central incisors due to erupting lateral incisor and canine crowns

Answer

As the maxillary lateral incisors and canines erupt, their follicles push the central incisor roots together, causing temporary crown flaring and midline diastema.

Question 4

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

Accepted Answer

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

Answer

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

Question 5

The 'leeway space' in the mixed dentition refers to the size difference between:

Accepted Answer

The combined primary canine and molars versus the combined permanent canine and premolars

Answer

Leeway space is the difference in combined mesiodistal widths of primary canines/first/second molars minus permanent canines/first/second premolars (approximately 1.5 mm upper, 2.5 mm lower per side).

American Board of Orthodontics (ABO) Practice Test

American Board of Orthodontics (ABO) Practice Test

ABO ABO Growth and Development