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: Dental
[{'content': 'A 45 year old female patient returns to your clinic with complaint of food lodgement in interproximal area of 47. On intraoral examination, 47 is restored with mesio-disto-occlusal amalgam restoration. Which type of matrix is used for this preparation? \nSelect and explain. \nA. Automatrix, B. Compound supported matrix, C. Universal matrix, D. Ivory matrix', 'role': 'user'}, {'content': 'Answer: A \nExplanation: When\xa0little\xa0tooth\xa0structure\xa0remains\xa0and\xa0deep\xa0gingival margins are present, the Tofflemire matrix may not function successfully, and the Automatrix system is beneficial.', 'role': 'assistant'}]