Tooth #12 has an occluso-mesial amalgam and the surrounding tooth structure has darkened. What is the cause?

Correct answer: D. Corrosion products of the amalgam diffusing into dentinal tubules

• A. Extrinsic stain is surface-level and removable by polishing.
• B. Pulpal necrosis darkens the whole crown uniformly, not just the tooth structure adjacent to the restoration.
• C. Recurrent caries is a differential to rule out, but generalized greyness around an old amalgam is most often corrosion.
• D. Correct. Tin and silver corrosion products migrate into the dentinal tubules over time, producing a grey-black discoloration visible through translucent enamel. This is a benign, expected finding — and it is what actually seals the amalgam margin.