Diffuse steel-gray, poorly demarcated discoloration
of mandibular mucosa.
Introduction: Amalgam Tattoo
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The implantation of dental materials into mildly injured or periodontally inflamed mucosal tissues during the restoration of carious teeth is not an unusual event. The material most likely to present as a mucosal discoloration is amalgam from the "silver fillings," hence, the lesion is usually called an amalgam tattoo, but other metals may produce the same effect. Most of the time these "biocompatible" materials do not illicit a local inflammatory response, but occasional cases are associated with chronic inflammatory changes compatible with a foreign body reaction. Amalgam is a combination of mercury, silver, tin, copper and, sometimes, zinc. The mercury usually comprises half of the mixture and rarely produces an obvious tissue necrosis despite its rather high level of toxicity in other settings. Overall, amalgam tattoo is found in approximately 1 per 1,000 adults (Table 1).
The amalgam tattoo presents as a soft, painless, nonulcerated, blue/gray/black macule with no surrounding erythematous reaction (two figures to left). It is most frequently found on the gingival or alveolar mucosa, but many cases are seen on the buccal mucosa and no anatomic site is immune from this change. The tattoo is found more frequently in females than in males, perhaps because women more frequently seek dental care. It is also seen more frequently with advancing patient age, presumably because of increased exposure to dental procedures over time. The tattoo is only moderately demarcated from the surrounding mucosa and is usually less than 0.5 cm. in greatest diameter, although rare examples have been more than 3.0 cm. in size. Lesions with larger particles will be visible on routine dental radiographs.
Some patients will demonstrate a long-term inflammatory response, with small discolored papules produced, and those who exhibit a strong macrophage response the discolored patch can enlarge over time as the macrophages engulf the foreign material and attempt to move it out of the area.
Occasional deposits of amalgam are found in bone, usually as a result of the material being inadvertently scraped from an adjacent restoration during tooth extraction of other surgical procedure, including the deliberate placement of amalgam into the apical canal of a root during endodontic surgery. These become quickly blackened and may impart a black discoloration to the adjacent bone.
The amalgam tattoo is characterized by an unencapsulated area of submucosal stroma with clusters of small black/brown rounded particles, often seen to coat blood vessels and reticulin fibers (first figure to left). Occasional larger, angular particles are seen, but seldom is there a noticeable inflammatory cell response. When present, this response is usually represented by chronic inflammatory cells aggregated in the areas of foreign material. Histiocytes and foreign body multinucleated giant cells may be associated with the amalgam particles, in which cases the lesion is said to be a foreign body reaction (second figure to left). The giant cells can surround or engulf the metallic particles, and sometimes huge pieces can be seen within their cytoplasm. Histiocytes also may be laden with the foreign material. Neutrophils and eosinophils are not part of this reaction.
When particles are numerous enough, a diffuse and sometimes intense fibrosis occurs in a wide region around them. This is especially noticeable when amalgam is embedded within bone marrow. The fibrosis may be quite avascular and is often without lymphocytes. The stroma around freshly embedded amalgam particles with show neovascularity and a more pronounced chronic inflammatory cell response.
Once present, the amalgam tattoo remains indefinitely, and occasional lesions slowly enlarge over time, presumably as amalgam-laden histiocytes try to move the material out of the local site. No treatment is necessary, but excisional biopsy is often performed in order to rule out melanoma or another pigmented lesion. Lesions visible on radiographs are usually not biopsied and those occurring on the visible vermilion border of the lips are usually removed for aesthetic reasons. There is no malignant potential for this lesion.
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* total examined population = 23,616 adults over 35 years of age