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: Radiology
[{'content': 'The following radiograph shows: \nSelect and explain. \nA. Fusion in 22, B. Gemination in 22, C. Concrescence in 22, D. Dilaceration in 21', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Gemination\nGeminated teeth are anomalies which arise from an attempt\xa0at the division\xa0of\xa0a\xa0single\xa0tooth\xa0germ\xa0by\xa0an\xa0invagination,\xa0with\xa0resultant\xa0incomplete\xa0formation\xa0of\xa0two\xa0teeth.\xa0The\xa0structure\xa0is usually one with two completely or incompletely separated\xa0crowns\xa0that\xa0have\xa0a\xa0single\xa0root\xa0and\xa0root\xa0canal.\xa0It\xa0is\xa0seen\xa0in\xa0deciduous as well as permanent dentition, and in some reported\xa0cases, appears to exhibit a hereditary tendency. It is not always\xa0possible\xa0to\xa0differentiate\xa0between\xa0gemination\xa0and\xa0a\xa0case\xa0in\xa0which there has been a fusion between a normal tooth and a\xa0supernumerary tooth.\nRadiological signs\nThe tooth has a notched incisal margin with a confluent or partially joined pulp canal system.', 'role': 'assistant'}]