Inhalation Sedation — ORE Part 1 MCQ
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Correct answer: C — Nitrous oxide and oxygen (N₂O/O₂)
Explanation lettering: D = shown as A · C = shown as B · A = shown as C · E = shown as D · B = shown as E
The correct answer is A: Nitrous oxide and oxygen (N₂O/O₂). Inhalation sedation with N₂O/O₂ is the standard, evidence-based conscious sedation technique used in UK paediatric dentistry. The mixture is administered in a variable, titrated concentration (typically 30–70% N₂O) via a nasal mask, allowing adjustment to the individual patient's needs. Option C (Entonox) is a plausible but incorrect distractor: Entonox is a fixed 50:50 premixed product licensed for acute analgesia (emergency care, labour), not for dental sedation, which requires titration of N₂O concentration. Options B and D (volatile anaesthetics sevoflurane and desflurane) are used in general anaesthesia, not conscious sedation, and are not suitable for dental office-based sedation in the UK. Option E is implausible. This item tests discrimination between conscious sedation and general anaesthesia, and between fixed-ratio and variable-ratio gas delivery—key knowledge for UK dental practice.
Reference: Scottish Dental Clinical Effectiveness Programme and Intercollegiate Advisory Committee for Sedation in Dentistry, cited in Lyne A, Ahmad S, Ashley P. Reducing the environmental impact of nitrous oxide in dentistry: a national quality improvement project. Br Dent J. 2026 Jan 23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12830357/