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
Most common side effect of vital teeth bleaching: 
Select and explain. 
A. Cervical resorption, B. Discoloration, C. Apical periodontitis, D. Apical root resorption
C: Apical periodontitis
Answer: C: Apical periodontitis 
Explanation: 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.