The efficacy of five techniques for removing root filling material: Microscopic versus radiographic evaluation

Aim To test and compare the efficacy of five methods for the removal of root filling material and to test the hypothesis that radiographs fail to represent the real extent of remaining material on canal walls. Methodology Fifty maxillary anterior single-rooted teeth with straight root canals were selected. The coronal third of each root canal was prepared with Gates-Glidden drills to number 3, whilst the apical two-thirds were prepared with manual K-files to size 40. Root fillings were performed using lateral compaction with gutta-percha and AH-26. After full setting, the coronal third of the root filling was removed with Gates-Glidden drills and the teeth divided into five groups (n=10). The remaining root filling material was then removed with either Hedström files and chloroform (25μL), using size 40 as the last file, SafeSider files, using a NiTi Pleezer reamer with a 0.06 taper followed by size 40 reciprocating file, with or without chloroform, or ProTaper Universal retreatment files (D2, D3) with or without chloroform. Reaching working length with no more gutta-percha on the last file was defined as the endpoint for all procedures. The presence of remaining filling material was first evaluated radiographically and then by the microscopic evaluation of split roots. The time required to accomplish the procedure was also recorded. anova and anova with repeated measures were used for statistical analysis of the results. Results Overall, 11-26% 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<0.01); 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. Conclusions All methods left root canal filling material on the canal walls. Radiographic evaluation failed to detect the extent of remaining root filling material, which could only be detected using microscopy.