Overview and definition
Amalgam tattoo is a benign, iatrogenic post-treatment finding, not a neoplasm, resulting from inadvertent implantation of dental amalgam particles into oral soft tissue.[1][2] It is the most common exogenous pigmentation of the oral mucosa and is also termed localized argyria or local argyrosis.[3][4] Lesions are asymptomatic, flat (macular), and range from blue-gray to black or brown, typically discovered incidentally on routine examination.[3][5] Prevalence in the general population is estimated at roughly 1–3%.[5] Deposition occurs during restoration placement, apicoectomy with retrograde amalgam fill, crown preparation, or tooth extraction, so lesions cluster near restored, endodontically treated, or previously extracted teeth.[5] Reported sites include gingiva and alveolar mucosa, buccal mucosa, floor of mouth, and vestibule, though any mucosal surface may be involved.[3][5] A slight female predilection (about 1.8:1) has been described.[3]
Radiographic findings
Recognition: Larger amalgam fragments appear as discrete radiopaque (bright) flecks within soft tissue on periapical or panoramic imaging, correlating with the clinically pigmented area.[1][5] Radiographic confirmation can obviate biopsy when particles are visible.[3][5]
Location — maxilla vs. mandible: Deposits localize to soft tissue adjacent to the implicated tooth or healed site in either arch; retrospective data identified the mandibular arch as the most common location.[2] Maxillary/palatal and maxillary gingival sites are regarded as higher-risk zones for melanoma, raising the threshold for radiographic-only diagnosis there.[3]
Normal variation and mimics: Many fine particles are submicroscopic and radiographically occult, so absence of radiopacity does not exclude the diagnosis.[6] Key differential diagnoses include graphite tattoo, focal melanosis, pigmented nevus, melanotic macule, thrombosed varix and, most critically, mucosal melanoma.[3][7] Particles may lie in lamina propria, submucosa, or deeper, occasionally within macrophages or giant cells, with variable or absent tissue reaction.[3][6]
Management and prognosis
Interpretation: A longstanding, stable, flat pigmentation near a restored or previously treated tooth with corresponding radiopacity is diagnostic, and no further treatment is required.[3][5] Clinical correlation with dental history (restorations, retrograde fills, extractions) supports the diagnosis.[5][7]
Red flags / referral: Biopsy is warranted when no radiopaque particles are identified, when the lesion arises suddenly, enlarges or changes, is remote from any restoration, or occupies a high-risk melanoma site.[3][5] Excision is otherwise elective and cosmetic, with favorable long-term outcomes and no reported recurrence after complete removal.[7][8] Prognosis is benign.