Have a question for the dental guru's on the board:

Had a patient come in with a decayed #3 that had a magnificent radiographic
looking RCT done. Unknown to me until I attempted to place a post/core
buildup in it [lets now debate whether or not it needed a post, lets say my
clinical judgment was good and IT DID NEED ONE], it was a thermafil palatal
canal fill.
I did not recognize it until I took my #1 flexi post reamer to the canals
and nothing would happen. I then took a small #2 Peezo and removed Gutta
percha only to find the plastic carrier still in the canal.

How do you restore Thermafil filled canals if a post core is needed???