The study involved 50 maxillary anterior single-rooted teeth with straight root canals. The coronal third of each root canal was prepared with Gates Glidden drills to number 3, and the apical two thirds were prepared with manual K-files to size 40. Roots were filled using lateral compaction with gutta-percha and AH-26. After the filling materials fully set, the coronal third of the filling was removed with Gates Glidden drills and the teeth were divided into 5 groups (n = 10). The remaining root filling material was then removed with one of the following methods: (1) Hedström files and chloroform (25 μL); (2) using size 40 as the last file; (3) SafeSider files; (4) a NiTi Pleezer reamer with a 0.06 taper followed by size 40 reciprocating file with or without chloroform; (5) ProTaper Universal retreatment files (D2, D3) with or without chloroform. The end point of all procedures was defined as reaching working length with no more gutta-percha on the last file. The presence of remaining filling material was first evaluated radiographically and then by the microscopic evaluation of split roots. The time required to finish the procedure was also recorded.
The study found that overall, 11% to 26% of the canal wall remained covered with filling material; no significant difference was found between the groups. The mechanized methods were faster than manual removal of filling material (P < .01); the use of solvent did not speed up the mechanized procedures. Radiographic evaluation failed to adequately and reliably detect the extent of filling material remaining on the canal walls, which was later observed by microscopic evaluation.
(Source: Kfir A et al. "The Efficacy of Five Techniques for Removing Root Filling Material: Microscopic Versus Radiographic Evaluation." International Endodontic Journal; doi: 10.1111/j.1365-2591.2011.01944.x; this article was first published online September 8, 2011)