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': 'If the maxillary canine is denoted as 23, which of the following tooth numbering systems was used? \nSelect and explain. \nA. Palmer system, B. Zsigmondy system, C. Universal system, D. FDI system', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The FDI two-digit system was introduced in 1970 by the Federation Dentaire Internationale (now known as the FDI World Dental Federation). It is a wholly digital system of tooth notation that makes visual sense, cognitive sense, and computer sense. This notation is also known as ISO-3950 notation.\nFDI World Dental Federation notation is widely used by dentists internationally to associate information to a specific tooth.\xa0\nOrientation of the chart is traditionally "dentist\'s view", i.e. patient\'s right corresponds to notation chart left. The designations "left" and "right" on the chart, however, nonetheless correspond to the patient\'s left and right, respectively.', 'role': 'assistant'}]