Lead line in gingival tooth border

This man with severe lead poisoning has a "lead line," a bluish-gray thin line running along the gingival tooth border, which also has considerable plaque. It is best seen at the location of the arrow. In patients with poor oral hygiene, hydrogen sulfide released by bacteria in the gingival pockets may react with lead in the gingival circulation to produce lead sulfide, a precipitate that appears as a darkly pigmented blue-gray line.