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': 'Frontal resorption is caused due to: \nSelect and explain. \nA. Light continuous force, B. Heavy continuous force, C. Heavy interrupted force, D. Light interrupted force', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Frontal resorption (direct/periosteal/forward resorption)\n\nWith light continuous forces, the bone is resorbed directly by a frontal osteoclastic attack.\xa0\nThe first step in orthodontic tooth movement is the activation of osteoclasts.\nIn frontal resorption, resorption is initiated from the PDL side of the alveolar bone. It usually takes place after 2 days.', 'role': 'assistant'}]