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
The most common reason of replacement of dental restoration: 
Select and explain. 
A. Secondary caries, B. Tooth fracture, C. Restoration fracture, D. None of the above
A: Secondary caries
Answer: A: Secondary caries 
Explanation: The most common reason for the replacement of dental restorations is secondary caries at the gingival tooth-restoration margin.