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 highest mercury concentration in amalgam filling is found: 
Select and explain. 
A. At the margin of the restoration, B. In the centre of the restoration, C. In the deepest part of the restoration, D. None of the above
A: At the margin of the restoration
Answer: A: At the margin of the restoration 
Explanation: Mercury analysis of a large number of restorations reveals that the mercury content of the marginal areas averages between 2% to 3% higher than the bulk of the restoration. This is true regardless of the condensation method or the “dryness” of the increments used to build the restoration.
Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, 12th ed page no 352