Amalgam used for dental restoration may become embedded into the oral mucosa, resulting in a dark discoloration.


Mechanism: traumatic placement of the amalgam metal into soft tissue


Usual locations:

(1) gingiva (adjacent to restored tooth)

(2) alveolar mucosa

(3) buccal mucosa (opposite a restored tooth)

(4) floor of the mouth


Gross appearance: flat macule that is dark gray or blue


Microscopic appearance:

(1) coarse, irregular, dense fragments or fine, discrete granules

(2) chronic inflammation, sometimes with foreign body giant cells

(3) varying degrees of fibrosis


The larger fragments can be visualized on an X-ray of the mouth, while the finer granules may be too small to be seen.


Differential diagnosis:

(1) malignant melanoma


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