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': 'Crown en-masse fracture is: \nSelect and explain. \nA. Ellis 1 fracture, B. Ellis 2 fracture, C. Ellis 8 fracture, D. Ellis 7 fracture', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Class I: Simple fracture of the crown involving enamel.\nClass II: Extensive fracture of the crown, with considerable\xa0amount of dentin involved but no pulp exposure.\nClass III:\xa0Extensive fracture of the crown, with considerable amount of dentin involved, with pulp exposure.\nClass IV:\xa0Traumatized tooth becomes nonvital (with or without loss of crown structure).\nClass V:\xa0Tooth lost due to trauma.\nClass VI:\xa0Fracture of root with or without crown or root structure.\nClass VII:\xa0Displacement of the tooth without crown or root fracture.\nClass VIII:\xa0Fracture of crown en masse.\nClass IX:\xa0Fracture of deciduous teeth.', 'role': 'assistant'}]