NBDE Part II 3 — Questions and Answers
Question 1: Which of the following best describes the mechanism of action of fluoride in caries prevention?
- It kills all cariogenic bacteria immediately
- It forms fluorapatite, which is more resistant to acid dissolution than hydroxyapatite (Correct answer)
- It neutralizes plaque acids by raising oral pH
- It prevents salivary buffering
Correct answer: It forms fluorapatite, which is more resistant to acid dissolution than hydroxyapatite
Fluoride substitutes for hydroxyl groups in hydroxyapatite to form fluorapatite, which has a lower critical pH and is significantly more resistant to acid dissolution.
Question 2: A 55-year-old edentulous patient needs complete dentures. Which jaw relation record is taken first during the construction sequence?
- Centric relation
- Vertical dimension of occlusion (Correct answer)
- Protrusive relation
- Face-bow transfer
Correct answer: Vertical dimension of occlusion
Vertical dimension of occlusion (VDO) must be established before centric relation can be recorded, as the correct jaw separation is needed to make a reproducible record.
Question 3: Furcation involvement classified as Class II (Glickman) means:
- The furcation can be probed but not penetrated
- The probe enters the furcation but does not pass through (Correct answer)
- The probe passes completely through the furcation
- Furcation is clinically undetectable
Correct answer: The probe enters the furcation but does not pass through
Glickman Class II furcation involvement means the horizontal probe enters the furcation entrance but does not pass to the other side.
Question 4: When taking a periapical radiograph using paralleling technique, the primary benefit over bisecting angle is:
- Less radiation dose to the patient
- Reduced distortion and more accurate representation of tooth length (Correct answer)
- Easier patient positioning
- Better soft tissue visualization
Correct answer: Reduced distortion and more accurate representation of tooth length
The paralleling technique places the film parallel to the tooth's long axis, minimizing geometric distortion and providing accurate tooth length and bone level readings.
Question 5: A patient on warfarin therapy requires a simple extraction. Their INR is 2.3. The correct management is:
- Postpone extraction until INR normalizes to 1.0
- Proceed with extraction using local hemostatic measures (Correct answer)
- Request hospitalization for IV vitamin K before extraction
- Switch the patient to heparin bridging therapy
Correct answer: Proceed with extraction using local hemostatic measures
An INR ≤3.5 is acceptable for simple dental extractions; local hemostatic measures (gelatin sponge, pressure) are sufficient without altering anticoagulant therapy.
Question 6: In removable partial denture design, which component provides indirect retention?
- Major connector
- Rest on the abutment tooth (Correct answer)
- Retentive clasp arm
- Lingual bar
Correct answer: Rest on the abutment tooth
An occlusal rest placed on the opposite side of the fulcrum line from the extension base provides indirect retention by preventing the denture base from rotating away from the tissue.
Question 7: Which suture material is preferred for intraoral use because it resorbs without requiring removal?
- Silk
- Polyester (Mersilene)
- Polyglycolic acid (Vicryl) (Correct answer)
- Nylon (Prolene)
Correct answer: Polyglycolic acid (Vicryl)
Polyglycolic acid (Vicryl) is a synthetic absorbable suture that hydrolyzes over 60–90 days and is widely used intraorally to eliminate the need for suture removal.
NBDE Part II 3
Which of the following best describes the mechanism of action of fluoride in caries prevention?