Black line stain, also known as mesenteric stain, is most common in women and children, but can occur at all ages. It is composed primarily of gram-positive rods.1 Clinically, it appears as a continuous fine black line (with no appreciable thickness) that follows the gingival crest the rest of the mouth is clean, and the gingiva is healthy.1,3 It is found mainly on the lingual and proximal surfaces of maxillary posterior teeth. Its etiology is thought to be related to a natural tendency the stai