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
Each of the following drug regimens is likely to influence periodontal treatment planning EXCEPT 
Select and explain. 
A. Dexamethasone, B. Dicoumarol, C. Diphenhydramine, D. Nitroglycerine
C: Diphenhydramine
Answer: C: Diphenhydramine 
Explanation: None