X-rays fall short in detecting leftover gutta-percha

Radiographs don't adequately reveal the amount of root filling material that remains following a root canal, according to a study in the International Endodontic Journal (September 8, 2011).

Researchers from Tel Aviv University and Hadassa and Hebrew University compared five methods for removing root filling material and the ability of radiographs versus a microscope to determine the true extent of material that remains on canal walls following this procedure.

After selecting 50 maxillary anterior single-rooted teeth with straight root canals, the researchers prepared the coronal third of each root canal with Gates-Glidden drills to number 3. They then prepared the apical two-thirds 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 (25 µL), 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.

The presence of remaining filling material was first evaluated radiographically, then by microscopic evaluation of split roots. The time required to accomplish the procedure was also recorded.

Overall, 11% to 26% of the canal wall remained covered with filling material, with no significant difference found among the five groups. The mechanized methods were faster than manual removal of filling material (p < 0.01), and the use of solvent did not speed up the mechanized procedures.

Finally, "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," the researchers reported.

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