In cases where root canal treatment has failed and infection has recurred at the root tip, the old root canal filling needs to be removed and the canals re-cleaned (retreatment). Attempting to directly scrape away the hardened old gutta-percha material inside the canal with mechanical files can lead to root perforations. Therefore, special chemical solvents are used to soften the gutta-percha. The most commonly preferred solvents clinically are chloroform, xylene, or derivatives of the natural oil eucalyptus oil/D-limonene. When a few drops of solvent are instilled into the canal, the polymeric structure of the gutta-percha dissolves within seconds, turning into a jelly-like consistency. This softened mass is then completely removed from the canal using rotary or hand files, without damaging the root walls.
