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Galvanism — MFDS Part 1 MCQ

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ModerateDental MaterialsGalvanismMFDS Part 1

A patient experiences brief, sharp pain only when chewing after placement of a posterior amalgam restoration. The restoration contacts an opposing gold alloy crown during occlusion. Both teeth respond normally to pulp sensibility testing and show no periapical abnormality. Which mechanism best explains the pain?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — A galvanic current between the dissimilar metals, with saliva acting as the electrolyte

Explanation lettering: C = shown as A · E = shown as B · B = shown as C · A = shown as E

A is correct. Dissimilar metals with different electrode potentials can form a galvanic couple when they make occlusal contact, while saliva provides the ionic electrolyte. The resulting transient current can produce a brief, sharp painful sensation. The strict association with metal-to-metal contact and normal pulpal and periapical findings distinguish this from postoperative pulpal inflammation. Excessive cavity depth would usually cause thermal or persistent pulpal symptoms rather than pain confined to contact with another metal. Amalgam placed on vital dentine does not itself produce galvanism; a second dissimilar metal is required. A gold crown need not be fractured, and inadequate polishing may influence surface corrosion but does not alone explain a galvanic shock.

Reference: Walker RS, Wade AG, Iazzetti G, Sarkar NK. Galvanic interaction between gold and amalgam: effect of zinc, time and surface treatments. Journal of the American Dental Association. 2003;134(11):1463–1467. https://pubmed.ncbi.nlm.nih.gov/14664264/