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
In DMF index, F indicates a tooth with: 
Select and explain. 
A. Zinc oxide eugenol filling, B. Silver amalgam filling, C. Caries below an existing restoration, D. Permanent filling in a deciduous tooth
B: Silver amalgam filling
Answer: B: Silver amalgam filling 
Explanation: Indicates the number of permanent teeth that have been attacked by caries, but which have been restored to keep them in a healthy condition in mouth. 
A tooth may have several fillings, but it is counted as one tooth. 
If a tooth has a filling but shows evidence of recurrent decay, it is counted as a decayed tooth. (Option 3 is eliminated) 
Temporary restorations are considered as Decayed (Option 1 is eliminated)
Only permanent teeth are considered (Option 4 is eliminated).

Essentials of preventive and community dentistry
5th edition
Soben Peter