During re-treatment procedures, removing the gutta-percha dry (if possible) is preferred. Simply because it is less messy. But I often find myself use a bit of C-form (what we call chloroform in the office) specially when I have to negotiate the very last part of the gutta-percha close to the apex. I also use it quite often when I re-treat cases with carrier-based obturation material. And, what a mess that creates!
To get rid of this “soup” of gutta-percha from the access cavity and to continue working in a very clean and controlled environment, alcohol should be used as the next irrigant. It clumps up all the softened gutta-percha to the point that it can easily be rinsed off by water spray or picked off by instruments.
Once the gross removal of gutta-percha from the canals is complete with alternating use of C-form and alcohol, I usually use EDTA as it will continue to clean the remaining of the softened gutta-percha from the canal system.
What rotary instruments do you recommend for the removal of dry gutta percha?
I usually use ProTaper Universal Retreatment files. You can also use ProFiles at higher speed as well. I never use rotary files to remove carrier-based obturation material. I use C-form for these cases in order to retrieve the carrier in one piece.