Caries management, sedation, tumours and ergonomics

Correct answer: A. A deep lesion in a vital, asymptomatic tooth where complete excavation would likely expose the pulp

• A. Correct. Stepwise excavation is a two-visit technique for exactly this situation: infected dentine is removed, affected dentine is left, the cavity is sealed with calcium hydroxide, and the tooth is reopened after several months once reparative dentine has formed.
• B. A lesion simply reaching the dentino-enamel junction is routine and is managed by conventional excavation in a single visit.
• C. Irreversible pulpitis means the pulp cannot recover. The tooth needs root canal treatment or extraction, not a technique aimed at preserving vitality.
• D. A necrotic pulp is beyond preservation; leaving carious dentine over dead tissue accomplishes nothing.

Note: Selective (one-step) removal to soft dentine is increasingly favoured over the two-visit stepwise approach, with comparable or better pulp survival.

Correct answer: A. Propofol

• A. Correct — this is the exception. Propofol is a pure sedative-hypnotic. It produces excellent sedation and amnesia but has no analgesic property, which is why it is paired with an opioid.
• B. Morphine is the reference opioid analgesic and is also sedating.
• C. Fentanyl is a potent short-acting opioid providing both analgesia and sedation.
• D. Nitrous oxide is both anxiolytic and genuinely analgesic — one of the few agents that reliably does both.

Note: Benzodiazepines belong with propofol on the no-analgesia side: they sedate and produce amnesia but do not relieve pain.

Correct answer: C. Odontoma

• A. The adenomatoid odontogenic tumour does favour young females and the anterior maxilla, but it is much rarer than odontoma.
• B. The calcifying epithelial odontogenic tumour (Pindborg tumour) is rare and presents in middle age.
• C. Correct. The odontoma is by a wide margin the most common odontogenic tumour overall, and it is typically discovered in the first two decades — often as an incidental finding when a tooth fails to erupt.
• D. Ameloblastoma peaks in the third to fifth decades and is far less common, though it is the most common clinically significant one.

Note: Odontomas are now classified as developmental hamartomas rather than true neoplasms. Compound types occur anteriorly, complex types posteriorly.

Correct answer: D. Green or blue-green

• A. Black provides no complementary stimulus and simply removes light input.
• B. Bright white increases glare and worsens the strain.
• C. Red is the colour the eye has been saturated with; looking at more red does nothing to relieve the fatigue.
• D. Correct. Blue-green is the complement of the red of oral tissues. Shifting the gaze to a blue-green surface lets the fatigued retinal receptors recover and reduces the afterimage effect.

Note: This is why operatory walls, scrubs and bibs are so often blue-green.

Correct answer: B. Unmyelinated C fibres

• A. A-beta fibres carry touch, pressure and vibration, not pain.
• B. Correct. C fibres are small and unmyelinated, so they conduct slowly. They carry the second wave of pain — dull, burning, throbbing and hard to localise, characteristic of pulpal inflammation.
• C. A-alpha fibres are the largest, serving proprioception and motor function to skeletal muscle.
• D. A-delta fibres are thinly myelinated and fast. They carry sharp, well-localised first pain, including the response to cold testing.

Note: Clinically useful: sharp pain that stops when the stimulus is removed suggests A-delta and reversible pulpitis, while lingering dull pain suggests C-fibre involvement and irreversible pulpitis.