Many years ago, a variety of metallic compounds were used medicinally, but such medicaments are either no longer or rarely still in use. Ingestion of heavy metals or metal salts can be an occupational hazard since many metals are used in industry and in paints. Lead, mercury, and bismuth have all been shown to be deposited in oral tissue if ingested in sufficient quantities or over a long course of time.
These ingested pigments tend to extravasate from vessels in foci of increased capillary permeability such as inflamed tissues. Thus, in the oral cavity, the pigmentation is usually found along the free marginal gingiva, where it dramatically outlines the gingival cuff, resembling eyeliner. This metallic line has a gray to black appearance. The heavy metals may be associated with systemic symptoms of toxicity, including behavioral changes, neurologic disorders, and intestinal pain. This condition is now rarely seen.