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': 'Type of external root resorption that occurs in concussion and subluxation: \nSelect and explain. \nA. Surface resorption, B. Replacement resorption, C. Ankylosis resorption, D. Inflammatory root resorption', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Surface resorption:\xa0\n\nIt is non invasive process which occurs after luxation injury.\xa0\nSmall superficial resorption cavities occur within cementum and the outer dentin.\nIt is repair process of physical damage to calcified tissue by recruitment of\xa0 cells following removal of damaged tissues by macrophages.\n\nInflammatory resorption:\xa0\n\nThis resorption occurs as a result of the necrotic pulp becoming infected in the presence of severely damaged cementum.\xa0\nThis infected pulp allows bacterial toxins to migrate out through the dentinal tubules into the periodontal ligament causing resorption of both root and adjacent bone.\n\nReplacement resorption:\xa0\n\nReplacement resorption occurs when there is extensive damage to periodontal ligament and cementum.\xa0\nHealing occurs from the alveolar side creating a union between tooth and bone.\n\nTextbook of Endodontics Nisha Garg 3rd Ed P:', 'role': 'assistant'}]