Amalgam tattoos are a common, benign form of pigmentation found in the mouth that results from standard dental procedures. This localized discoloration, also known as focal argyrosis, is considered the most frequent extrinsic pigmented lesion of the oral mucosa. The presence of an amalgam tattoo, while often alarming to a patient who discovers it, does not pose a health risk. It is a permanent marker of past dental work and is typically discovered during routine dental examinations.
The Mechanism of Amalgam Implantation
Dental amalgam is the traditional “silver filling,” a robust alloy primarily composed of silver, tin, and copper, mixed with liquid mercury to create a moldable restorative material. The accidental introduction of these dental amalgam particles into the soft tissues of the mouth is the cause of the amalgam tattoo. The metal particles in the tattoo are not toxic, as the mercury is not in a free state.
The implantation of these metallic fragments can occur during several routine dental operations. Common scenarios include the high-speed removal of an old filling, forcing tiny particles into the surrounding gum tissue. Placement of a new amalgam filling or extraction of a tooth with an amalgam restoration can also leave metallic debris that embeds in the soft tissue or bone socket. Endodontic procedures, such as an apicoectomy where amalgam seals the root end, may also cause the surrounding gingiva to become tattooed.
Once embedded, the particles are too large for the body to clear completely, leading to permanent pigmentation. The silver component of the amalgam is the primary element responsible for the lasting discoloration. Macrophages, the body’s immune cells, attempt to engulf the foreign material, but the fine, dark silver granules become scattered throughout the connective tissue, resulting in the permanent tattoo.
Identifying the Physical Characteristics
The visual presentation of an amalgam tattoo is typically a flat, asymptomatic area of discoloration on the oral mucosa, known as a macule. The color ranges from a light bluish-gray to dark black, depending on the concentration and depth of the embedded metal particles. It does not cause pain or swelling and does not blanch, or lose color, when pressure is applied.
The most common location for this pigmentation is the gingiva, or gums, particularly in the lower jaw near a current or former amalgam-restored tooth. The alveolar mucosa (tissue covering the jawbone) and the buccal mucosa (the inside of the cheek) are also frequent sites. The size can vary from a pinhead to several millimeters, and the borders may be either well-defined or appear irregular and diffuse.
Differential Diagnosis and Management
While amalgam tattoos are benign, their dark appearance necessitates a careful evaluation to differentiate them from other, more serious pigmented lesions. The primary concern is ruling out mucosal melanoma, a rare but aggressive form of oral cancer. The lack of change in size or color over time is an important clinical indicator that the lesion is an amalgam tattoo.
A dental professional will often make a preliminary diagnosis based on the tattoo’s appearance and its proximity to a tooth with an amalgam filling. Radiography, or X-ray imaging, is a helpful diagnostic tool, as larger metallic fragments will appear bright white (radio-opaque) within the soft tissue, confirming the presence of amalgam. However, the absence of a visible fragment on a radiograph does not exclude an amalgam tattoo, as the particles may be too small or too dispersed to be detected.
If the lesion is located away from a dental restoration, has changed in size or color, or if a definitive diagnosis cannot be made with clinical and radiographic examination, a biopsy is performed. The biopsy allows for a microscopic analysis to confirm the presence of metal particles and definitively rule out malignancy. Since amalgam tattoos are harmless, no treatment is required in most cases, but if the patient is concerned about aesthetics, the lesion can be removed through surgical excision or laser ablation.