MJDF Orthodontics 2 — Questions and Answers
Question 1: Which type of orthodontic tooth movement involves the entire tooth, including the root apex, moving in the same direction without tipping?
- Tipping
- Bodily (translation) movement (Correct answer)
- Torque
- Rotation
Correct answer: Bodily (translation) movement
Bodily movement (translation) requires the crown and root apex to move equally in the same direction, requiring a force couple and being the most demanding biomechanically.
Question 2: Current best evidence regarding the duration of orthodontic retention after fixed appliance therapy recommends:
- 3 months of night-time wear
- 6 months of full-time wear
- 12 months then cessation
- Indefinite retention (Correct answer)
Correct answer: Indefinite retention
Current evidence supports indefinite retention, as relapse can occur many years post-treatment and no predictable safe end-point for cessation has been established.
Question 3: Which force type is considered optimal for efficient orthodontic tooth movement with minimal tissue damage?
- Heavy continuous force
- Light intermittent force
- Light continuous force (Correct answer)
- Heavy intermittent force
Correct answer: Light continuous force
Light continuous forces optimise bone remodelling via sustained periodontal ligament stimulation without causing hyalinisation or undermining resorption.
Question 4: The Hawley retainer is best classified as which type of orthodontic appliance?
- Fixed functional appliance
- Removable retainer (Correct answer)
- Fixed lingual retainer
- Myofunctional regulator
Correct answer: Removable retainer
The Hawley retainer is a removable appliance comprising an acrylic baseplate and labial bow, widely used for post-treatment retention.
Question 5: Extraoral anchorage in orthodontics refers to:
- Using teeth in both arches to resist forces
- Using soft tissue anchorage from the tongue
- Using structures outside the oral cavity such as the head or neck to reinforce anchorage (Correct answer)
- Implant-supported anchorage within the jaw bone
Correct answer: Using structures outside the oral cavity such as the head or neck to reinforce anchorage
Extraoral anchorage involves headgear attached to the head or neck to provide force resistance or to redirect growth, supplementing intraoral anchorage.
Question 6: A hyperdivergent skeletal facial pattern is characterised by:
- Reduced lower facial height and a flat mandibular plane angle
- Increased lower facial height and a steep mandibular plane angle (Correct answer)
- Prominent cheekbones with deep overbite
- Retrognathic maxilla with normal mandibular plane angle
Correct answer: Increased lower facial height and a steep mandibular plane angle
Hyperdivergent patients have a steep mandibular plane angle and increased lower facial height, often associated with anterior open bite tendency.
Question 7: The primary mechanism by which functional appliances achieve their effect is:
- Direct mechanical forces applied to individual teeth
- Redirecting condylar growth by posturing the mandible forward (Correct answer)
- Applying torquing forces to root apices
- Suture expansion of the midpalatal suture
Correct answer: Redirecting condylar growth by posturing the mandible forward
Functional appliances hold the mandible in a protrusive position, transmitting muscle and stretch forces to stimulate adaptive condylar growth and dental compensation.
MJDF Orthodontics 2
Which type of orthodontic tooth movement involves the entire tooth, including the root apex, moving in the same direction without tipping?