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': 'Most common side effect of vital teeth bleaching: \nSelect and explain. \nA. Cervical resorption, B. Discoloration, C. Apical periodontitis, D. Apical root resorption', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Cervical resorption is a common consequence of bleaching of non-vital teeth whereas apical periodontitis is a common sequel of bleaching of vital teeth. The possibility of cervical resorption can be reduced by sealing the root canal orifice with cavit to prevent percolation of bleaching agent or by keeping a paste of calcium hydroxide and sterile water in the pulp chamber.', 'role': 'assistant'}]