Start practicing

Anatomy & Histology · patient case with 3 questions

Cranial nerves, radiation safety and the diabetic patient

Scenario: Three items spanning anatomy, radiology and medicine.

Question 1

All of the following cranial nerves participate in swallowing EXCEPT:

  1. XI (accessory)
  2. VII (facial)
  3. IX (glossopharyngeal)
  4. X (vagus)
Show answer and explanation

Correct answer: A. XI (accessory)

  • A. Correct — this is the exception. The accessory nerve supplies sternocleidomastoid and trapezius, muscles of head and shoulder movement. It plays no part in the swallow.
  • B. The facial nerve does participate: it supplies the muscles that seal the lips and control the oral phase, along with the posterior belly of digastric and stylohyoid.
  • C. The glossopharyngeal nerve does participate: it carries sensation from the oropharynx that triggers the swallow reflex and supplies stylopharyngeus.
  • D. The vagus does participate, supplying the pharyngeal constrictors and the muscles of the soft palate and larynx through the pharyngeal plexus.

Note: Trigeminal (V) and hypoglossal (XII) are also involved — V for the muscles of mastication and mylohyoid, XII for tongue movement.

Permanent page for this question

Question 2

Following the ALARA principle, which radiographic examination would you select for a routine patient?

  1. A cone beam CT
  2. An MRI
  3. Bitewings and periapicals as indicated
  4. A panoramic radiograph
Show answer and explanation

Correct answer: C. Bitewings and periapicals as indicated

  • A. CBCT delivers substantially more radiation and is justified only for specific three-dimensional questions such as implant planning, impacted teeth or complex endodontic anatomy.
  • B. MRI uses no ionising radiation at all, but it images soft tissue and is not a substitute for dental radiography.
  • C. Correct. ALARA — as low as reasonably achievable — means selecting the smallest examination that answers the clinical question. Intraoral films selected on the basis of the examination deliver the least dose for the most diagnostic yield.
  • D. A panoramic film has its place for a broad survey, but it lacks the resolution to detect interproximal caries or assess bone levels precisely.

Permanent page for this question

Question 3

All of the following may be used for gingival displacement in a diabetic patient EXCEPT:

  1. Aluminium chloride
  2. Plain retraction cord with a mechanical technique
  3. Epinephrine-impregnated cord (1:50,000)
  4. Ferric sulfate
Show answer and explanation

Correct answer: C. Epinephrine-impregnated cord (1:50,000)

  • A. Aluminium chloride is a safe and widely used astringent that works by protein precipitation and local vasoconstriction without systemic effect.
  • B. Plain cord used mechanically causes displacement by physical pressure alone and carries no pharmacological risk.
  • C. Correct — this is the exception. Racemic epinephrine cord delivers a substantial systemic dose through the abraded sulcus. It is contraindicated in diabetes, cardiovascular disease, hyperthyroidism and in patients on certain antidepressants.
  • D. Ferric sulfate is also acceptable, with good haemostasis. Its only real drawback is transient tissue staining and its inhibition of resin polymerisation.

Permanent page for this question

Practice patient cases Anatomy & Histology study notes