ABO Orthodontic Biomechanics 3

Question 1

Frontal (direct) bone resorption during tooth movement occurs when applied force is:

Accepted Answer

Light and preserves PDL vitality

Answer

Light forces maintain PDL vitality, allowing osteoclasts to resorb bone directly on the pressure side.

Question 2

Undermining (indirect) resorption is associated with:

Accepted Answer

Hyalinization of the PDL from excessive force

Answer

Excessive force causes PDL hyalinization, and resorption proceeds indirectly from adjacent marrow spaces, delaying movement.

Question 3

During tooth movement, cells responsible for bone formation on the tension side are:

Accepted Answer

Osteoblasts

Answer

On the tension side, stretched PDL fibers stimulate osteoblasts to deposit new bone.

Question 4

A longer lag phase in the tooth-movement timeline is typically caused by:

Accepted Answer

Areas of hyalinization requiring undermining resorption

Answer

Hyalinized zones must be removed by undermining resorption before movement resumes, creating a lag phase.

Question 5

Which structure primarily transmits orthodontic force signals into cellular bone remodeling?

Accepted Answer

The periodontal ligament

Answer

The PDL senses mechanical strain and mediates the biological remodeling of surrounding alveolar bone.

American Board of Orthodontics (ABO) Practice Test