Amalgam tattoo (amalgam pigmentation) of the oral mucosa: clinical manifestations, diagnosis and treatment.

Amalgam tattoo is an iatrogenic lesion caused by traumatic implantation of dental amalgam into soft tissue. Amalgam tattoo is the most common localized pigmented lesion in the mouth. In a study of a mass screening oral examination in the United States, it was found in about 0.4-0.9% of the adult population and in Sweden in about 8%. Clinically, amalgam tattoo presents as a dark gray or blue, flat macule located adjacent to a restored tooth. Most are located on the gingiva and alveolar mucosa followed by the buccal mucosa and the floor of the mouth. Microscopic examination reveals that amalgam is present in the tissues in two forms: as irregular dark, solid fragments of metal or as numerous, discrete fine, brown or black granules dispersed along collagen bundles and around small blood vessels and nerves. In most lesions, it is presented in both forms. The biologic response to the amalgam is related to particle size, quantity and elemental composition of the amalgam. Large fragments often become surrounded by dense fibrous connective tissue. Smaller particles are associated with mild to moderate chronic inflammatory response with individual macrophages engulfing small amalgam particles. Occasionally, the reaction takes the form of foreign body granuloma in which macrophages and multinucleated giant cells are present. Some of the multinucleated giant cells also contain amalgam particles. Diagnosis of amalgam tattoo is usually obvious from the location and clinical appearance. A radiograph is recommended to confirm the presence of metallic particles, but absence of radiographic evidence does not rule out the possibility, since particles are often too fine or widely dispersed to be visible on radiographs. When there is no radiographic evidence or an adjacent restored tooth, biopsy is recommended to rule out an early melanoma. Once the diagnosis of amalgam tattoo has been established, no additional treatment is necessary except for cosmetic reasons. If the pigmentation is cosmetically unacceptable, surgical excision and transplantation of oral mucosal tissue has been suggested. Q-switched ruby laser and Q-switched alexandrite laser have also been used with favorable results.