The marginal sealing with galvanic corrosion products relates to which phenomenon?

• A. buildup of corrosion products
• B. oxygen diffusion
• C. discoloration
• D. thermal expansion mismatch

Answer: (A)

When two dissimilar metals are in contact in the mouth, saliva acts as an electrolyte and drives galvanic corrosion. The more active metal acts as the anode and corrodes, releasing metal ions and corrosion products. At the margin of a dental restoration, these products can accumulate and deposit as oxides, hydroxides, or other salts. This buildup at the marginal seal can disturb the smooth seal, promote roughness, and contribute to microleakage and staining. So the phenomenon described is the buildup of corrosion products at the margin caused by galvanic corrosion.

Oxygen diffusion may influence overall corrosion behavior but doesn’t define the specific marginal deposition process. Discoloration can be a consequence of corrosion products but isn’t the process itself. Thermal expansion mismatch relates to mechanical stress at the interface, not to the formation and accumulation of corrosion products.