Desensitising Toothpaste Mechanism — ORE Part 1 MCQ
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Correct answer: B — It reduces intradental nerve excitability by sustained depolarisation
Explanation lettering: D = shown as A · A = shown as B · B = shown as C · C = shown as D
A is correct. Potassium nitrate acts principally as a neural desensitising agent. Potassium ions are proposed to enter exposed dentinal tubules and raise extracellular potassium concentration around intradental nerve endings. This maintains depolarisation and reduces nerve excitability, making pain impulses less likely in response to thermal, tactile or osmotic stimuli. B describes tubule-occluding technologies, such as stannous fluoride, arginine-containing systems or calcium sodium phosphosilicate, rather than potassium nitrate. C would tend to increase dentine permeability. D describes a mineralising effect, while E is not a recognised mechanism of potassium nitrate toothpaste. Although direct confirmation in intact human teeth is limited, neural depolarisation remains the accepted teaching mechanism.
Reference: Orchardson R, Gillam DG. The efficacy of potassium salts as agents for treating dentin hypersensitivity. Journal of Orofacial Pain. 2000;14(1):9-19. https://pubmed.ncbi.nlm.nih.gov/11203743/