system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
In DMF index, F indicates a tooth with:
assistant
The correct answer is  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