NBDE MCQ 4 — Questions and Answers
Question 1: Which nerve provides sensory innervation to the anterior two-thirds of the tongue?
- Glossopharyngeal nerve (CN IX)
- Lingual nerve (branch of CN V3) (Correct answer)
- Chorda tympani (branch of CN VII)
- Hypoglossal nerve (CN XII)
Correct answer: Lingual nerve (branch of CN V3)
The lingual nerve, a branch of the mandibular division of the trigeminal nerve, carries general somatic afferent (touch, pain, temperature) information from the anterior two-thirds of the tongue.
Question 2: Nitrous oxide exerts its analgesic effect primarily through:
- Opioid receptor agonism
- GABA-A receptor potentiation
- NMDA receptor antagonism (Correct answer)
- Sodium channel blockade
Correct answer: NMDA receptor antagonism
Nitrous oxide produces analgesia mainly by antagonizing NMDA (N-methyl-D-aspartate) glutamate receptors, reducing pain signal transmission in the CNS.
Question 3: Which radiographic technique minimizes distortion and projects teeth at their true length?
- Bisecting angle technique
- Paralleling technique (Correct answer)
- Occlusal technique
- Panoramic technique
Correct answer: Paralleling technique
The paralleling technique places the film parallel to the tooth's long axis with the central ray perpendicular to both, producing minimal geometric distortion.
Question 4: In the formation of dentin, which organic component constitutes approximately 90% of dentin matrix?
- Proteoglycans
- Type I collagen (Correct answer)
- Dentin sialoprotein
- Osteocalcin
Correct answer: Type I collagen
Type I collagen comprises approximately 90% of dentin's organic matrix, providing the scaffold upon which hydroxyapatite crystals are deposited.
Question 5: A patient on warfarin therapy requires a routine extraction. The INR result is 3.8. The appropriate course of action is:
- Proceed with extraction using local hemostatic measures
- Extract without modification
- Postpone and consult physician to adjust anticoagulation (Correct answer)
- Administer vitamin K immediately and extract same day
Correct answer: Postpone and consult physician to adjust anticoagulation
An INR of 3.8 is above the safe threshold of 3.5 for dental extractions; elective procedures should be postponed and the physician consulted to adjust dosing.
Question 6: Which of the following is the FIRST sign of local anesthetic toxicity affecting the CNS?
- Seizures
- Circumoral numbness and lightheadedness (Correct answer)
- Respiratory arrest
- Loss of consciousness
Correct answer: Circumoral numbness and lightheadedness
Early CNS excitatory signs of local anesthetic toxicity include circumoral numbness, tingling, lightheadedness, and tinnitus before progression to seizures.
Question 7: The Angle Class II, Division 2 malocclusion is characterized by:
- Mesially positioned mandibular first molar with protruded maxillary incisors
- Distally positioned mandibular first molar with retroclined maxillary central incisors (Correct answer)
- Mesially positioned mandibular first molar with retroclined maxillary incisors
- Distally positioned mandibular first molar with proclined maxillary lateral incisors
Correct answer: Distally positioned mandibular first molar with retroclined maxillary central incisors
Class II Division 2 features a distal molar relationship (Class II) with retroclined (lingually inclined) maxillary central incisors and often proclined lateral incisors.
NBDE MCQ 4
Which nerve provides sensory innervation to the anterior two-thirds of the tongue?