This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Burtonian line around the gingiva is caused by the absorption of: \nSelect and explain. \nA. Lead, B. Copper, C. Mercury, D. Bismuth', 'role': 'user'}, {'content': "Answer: A \nExplanation: Oral Manifestations:\xa0The formation of a ‘lead line’ similar to the 'bismuth line’ occurs in lead poisoning. This gray or bluish black line of sulfide pigmentation occurs in the\xa0gingiva, but is somewhat more diffuse than that of bismuth.\xa0It is also found occasionally in other areas of the oral cavity.\xa0Ulcerative stomatitis is an additional reported finding.\nExcessive salivation and a metallic taste are also common\xa0complaints in this condition, as is swelling of the salivary\xa0glands. It is reported by Altshuller and his associates that lead\xa0is deposited in the deciduous teeth of children suffering from\xa0lead poisoning, and that those teeth may serve as an index of the body burden of lead.\nKey concept:\nBurton's line, also known as the Burton line or Burtonian line, is a clinical sign found in patients with chronic lead poisoning. It is a very thin, black-blue line visible along the margin of the gums.\nRef - Shafers 7th Ed P:558", 'role': 'assistant'}]