In DMF index, F indicates a tooth with:

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