ABO ABO Retention and Stability 1 — Questions and Answers
Question 1: Which factor is most commonly cited as a cause of post-treatment lower incisor crowding recurrence?
- Excessive torque applied during treatment
- Late mandibular growth and forward drift of lower teeth (Correct answer)
- Use of full-coverage retainers
- Expansion of the upper arch
Correct answer: Late mandibular growth and forward drift of lower teeth
Late mandibular growth combined with anterior soft tissue pressure and mesial drift causes lower incisor crowding to recur after treatment.
Question 2: A Hawley retainer differs from a clear vacuum-formed retainer primarily in that it:
- Cannot be adjusted after delivery
- Allows minor tooth movement and easy modification by the clinician (Correct answer)
- Covers the occlusal surfaces completely
- Is bonded to the teeth
Correct answer: Allows minor tooth movement and easy modification by the clinician
Hawley retainers have a labial bow that can be adjusted by the clinician, allowing minor tooth movement corrections during the retention phase.
Question 3: Which type of teeth movement has the LEAST long-term stability after orthodontic treatment?
- Molar intrusion
- Expansion of the lower intercanine width (Correct answer)
- Upper incisor retraction
- Molar distalization with headgear
Correct answer: Expansion of the lower intercanine width
Expansion of the lower intercanine width is highly unstable because it is strongly determined by the pre-treatment dimensions and muscular environment.
Question 4: A fixed lingual retainer bonded from canine to canine on the lower arch is most effective for:
- Preventing molar rotation
- Maintaining lower incisor and canine alignment long-term (Correct answer)
- Retaining expanded arch width
- Preventing deep bite relapse
Correct answer: Maintaining lower incisor and canine alignment long-term
Bonded lingual retainers attached canine-to-canine are highly effective at preventing lower anterior crowding relapse.
Question 5: The fibrotomy (circumferential supracrestal fiberotomy, CSF) procedure is performed to:
- Accelerate tooth movement
- Reduce relapse of rotational corrections by severing the supracrestal fibers (Correct answer)
- Increase alveolar bone density
- Improve periodontal health
Correct answer: Reduce relapse of rotational corrections by severing the supracrestal fibers
CSF severs the supracrestal gingival fibers that tend to pull rotated teeth back toward their original position after correction.
Question 6: Which patient characteristic is associated with the GREATEST risk of orthodontic relapse?
- Adult age at treatment start
- Mild crowding prior to treatment
- Extraction of all four premolars
- Skeletal discrepancy that was not fully corrected (Correct answer)
Correct answer: Skeletal discrepancy that was not fully corrected
When the underlying skeletal discrepancy is not fully corrected, continued jaw growth and soft tissue pressure tend to drive teeth back toward the original malocclusion.
ABO ABO Retention and Stability 1
Which factor is most commonly cited as a cause of post-treatment lower incisor crowding recurrence?