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
Which one of the following is not FDA approved 
Select and explain. 
A. GEM 215, B. Elyzol, C. Periochip, D. Atridox
B: Elyzol
Answer: B: Elyzol 
Explanation: None