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': 'Microabrasion techniques for elimination of discoloration of teeth work by: \nSelect and explain. \nA. Removing surface enamel, B. Bleaching stains, C. Bleaching developmental defects, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Surface discolorations\xa0because\xa0of\xa0fluorosis can\xa0also\xa0be\xa0removed by microabrasion, if the discoloration is within 0.2\xa0to 0.3 mm removal depth limit.\nIn 1984, McCloskey reported\xa0the use\xa0of\xa018%\xa0HCI swabbed on\xa0teeth for\xa0the removal\xa0of\xa0superficial\xa0fluorosis\xa0stains.\xa0\nSubsequently,\xa0in 1986, Croll\xa0modified\xa0the\xa0technique to include the use of pumice with\xa0the HCl to form a paste applied with a tongue blade.', 'role': 'assistant'}]