Stephan Curve — NDEB AFK MCQ
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Correct answer: A — The pH drop in dental plaque following carbohydrate exposure and subsequent recovery
The Stephan curve (Robert Stephan, 1944) demonstrates that following exposure to fermentable carbohydrates, plaque pH drops rapidly from resting levels (~6.5-7.0) to below the critical pH for enamel demineralisation (~5.5) within 2-5 minutes, reaching a nadir at approximately 5-20 minutes. The pH then gradually returns to resting levels over 30-60 minutes as salivary buffers neutralise the acids and bacteria metabolise remaining substrate. Frequent carbohydrate exposure prolongs the time below critical pH.
Reference: Fejerskov & Kidd – Dental Caries: The Disease and Its Clinical Management, 3rd ed., 2015