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Orthodontics: INBDE study notes and practice questions

Orthodontics questions ask you to classify a bite, read basic cephalometric values, decide when to refer or intervene in a growing child, and understand how teeth move.

161 practice questions · 3 patient cases

Practice Orthodontics

Where it fits in the official INBDE blueprint

Oral Health Management (occlusal problems). Nearest foundation knowledge areas: FK 1, FK 4. See the content outline for the official weights. This mapping is approximate: real items combine a clinical area with a foundation area.

What this area tests

High-yield checklist

Common traps

These notes are original study aids, not official exam content. Confirm clinical details against current guidelines.

Sample questions

1. A patient is missing tooth #19, and tooth #18 is mesialized. What would happen if a coil spring is used?

  1. Extrusion and mesialization of #18
  2. Intrusion and mesialization of #18
  3. Extrusion and distalization of #18
  4. Distalization of #18 with no extrusion
Show answer and explanation

Correct answer: C. Extrusion and distalization of #18

A coil spring applies force to reposition teeth. In this case, it would exert distal force on #18, causing distalization. Due to the angulation of the root and force application, extrusion (movement outward from the socket) may also occur. Proper orthodontic planning is essential to prevent unintended movements.

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2. Which periodontal fibers are responsible for tooth relapse/rotation after orthodontic treatment?

  1. Transseptal fibers
  2. Gingival fibers (circular/dentogingival)
  3. Apical fibers
  4. Alveolar crest fibers
Show answer and explanation

Correct answer: B. Gingival fibers (circular/dentogingival)

✓ B) Gingival fibers (particularly the supracrestal/free gingival fibers) are correct.
The supracrestal (free gingival/circular) fibers are the primary cause of rotational relapse after orthodontics. These fibers have 'elastic memory' and are not remodeled as quickly as the alveolar bone PDL fibers. They pull teeth back toward their original position. Fiberotomy (circumferential supracrestal fiberotomy/CSF) — surgically severing these fibers — helps prevent rotational relapse. Transseptal fibers maintain interproximal contact but are less responsible for rotation.

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3. When an uprighting spring coil is used to upright a mesially tipped mandibular second molar (#18), what is the typical biomechanical result?

  1. Crown tips distally and the tooth extrudes
  2. Root moves mesially and the tooth intrudes
  3. Root moves mesially and the tooth extrudes
  4. Crown tips distally and the tooth intrudes
Show answer and explanation

Correct answer: A. Crown tips distally and the tooth extrudes

An uprighting spring applies a tipping force to upright a mesially tilted molar. Because the force is applied at the crown level without controlling the root apex separately, the result is a simple tipping movement: the crown tips distally (toward the desired upright position) while the root tends to move mesially. Additionally, since the point of force application (the bracket/band) is occlusal to the center of resistance of the tooth, the moment created tends to extrude the tooth. To achieve true bodily uprighting or controlled root movement with minimal extrusion, additional mechanics (intrusive forces, tip-back bends, or skeletal anchorage) are required.

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4. A 70-year-old patient wishes to improve the appearance of their teeth. All of the following are appropriate treatment options EXCEPT:

  1. Orthodontic braces
  2. Dental veneers
  3. Serial extraction
  4. Invisalign (clear aligner therapy)
Show answer and explanation

Correct answer: C. Serial extraction

Serial extraction is a planned, sequential extraction of deciduous and sometimes permanent teeth over time to guide the eruption of permanent teeth and alleviate crowding. It is a pediatric orthodontic procedure performed in children aged 8-12 years during mixed dentition, not in adult patients. A 70-year-old patient would have no deciduous teeth remaining, making serial extraction irrelevant and inappropriate. Orthodontic braces, veneers, and Invisalign are all appropriate esthetic options for adult patients.

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5. An 8-year-old patient has a diastema between the maxillary central incisors. What is most likely to happen?

  1. The diastema will increase in size after the other teeth erupt
  2. The diastema will close if it was less than 2 mm, once the rest of the teeth erupt
  3. The diastema will close even if it was more than 2 mm
  4. The diastema will not change
Show answer and explanation

Correct answer: B. The diastema will close if it was less than 2 mm, once the rest of the teeth erupt

The classic 'ugly duckling stage' diastema in the mixed dentition commonly self-resolves as the lateral incisors and especially the canines erupt and migrate mesially, closing the space — but this favorable spontaneous closure is most reliably expected when the diastema is smaller (often cited as under about 2mm); larger diastemas are less likely to fully close spontaneously and may need orthodontic evaluation/intervention.

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6. A patient has rotated maxillary anterior teeth. All of the following are valid reasons a removable Hawley-type retainer would be a poor choice EXCEPT:

  1. The severity/degree of rotation present
  2. Poor oral hygiene (this is actually a reason to favor a removable appliance, since it can be taken out for cleaning — not a reason against it)
  3. Unfavorable tooth angulation limiting passive appliance seating
  4. The need for active orthodontic correction of the rotation, which a passive retainer cannot provide
Show answer and explanation

Correct answer: B. Poor oral hygiene (this is actually a reason to favor a removable appliance, since it can be taken out for cleaning — not a reason against it)

Severely rotated teeth, unfavorable angulation, and the need for active tooth movement (which requires an active appliance, not a passive retainer) are all legitimate reasons a Hawley retainer alone would be inadequate. Poor oral hygiene is actually an argument in FAVOR of a removable appliance (it can be removed for cleaning), making it the exception.

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7. On the TENSION side of orthodontic tooth movement, which cells are primarily active?

  1. Osteoclasts
  2. Chondroblasts
  3. Fibroblasts
  4. Osteoblasts
Show answer and explanation

Correct answer: D. Osteoblasts

On the tension side, stretched PDL fibers signal osteoblasts to deposit new bone. Tension = bone formation; Pressure side = osteoclasts (resorption).
  • A. ❌ Osteoclasts are active on the PRESSURE side (bone resorbed to allow movement).
  • B. ❌ Chondroblasts produce cartilage; not involved in orthodontic bone remodeling.
  • C. ❌ Fibroblasts maintain PDL but are not the primary bone-forming cell on the tension side.
  • D. ✅ CORRECT – Tension side: osteoblasts deposit new bone.

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8. A patient's facial profile looks normal, but their occlusion is altered. Which dental condition is most likely?

  1. Dental crowding
  2. Skeletal overjet
  3. Skeletal overbite
  4. Posterior crossbite
Show answer and explanation

Correct answer: A. Dental crowding

A normal facial profile (soft tissue profile) suggests that the skeletal (jaw) relationships are normal. Altered occlusion without facial profile changes is most consistent with a dental discrepancy rather than a skeletal discrepancy. Dental crowding results from inadequate arch space relative to tooth size, causing malalignment without changing the jaw relationship or facial profile. Skeletal overjet or overbite would typically produce changes in the facial profile (e.g., retrusive chin, full lips). This distinction between dental versus skeletal malocclusion is fundamental in orthodontic diagnosis.

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Patient cases

All Orthodontics questions (161)