Removing fractured endodontic instruments with a modified tube technique using a light-curing composite

The aim of this in vitro study was to assess an alternative method using light-curing composite for removing fractured endodontic instruments with a tube technique.

Two different stainless steel endodontic instruments (ISO 20: Hedstrom files, K-files; VDW, Munich, Germany) were cut at the diameter of 0.4 mm. These fragments were fixed in a vise leaving a free end of 1 or 2 mm. Cyanoacrylate (Instant Fix; Henry Schein Dental, Melville, NY), dual-curing Rebilda DC (VOCO, Cuxhaven, Germany), and light-curing SureFil SDR (Dentsply, York, PA) were placed into microtubes (N'Durance Syringe Tips; Septodont, Saint-Maur, France) and shifted over the instruments (n = 20 in each group). After polymerization, pull-out tests were performed with a constant speed of 2 mm/min; failure load was measured digitally. Data were analyzed using the Kruskal-Wallis test followed by the Dunn test for pairwise comparison.

The median failure load was up to 62.5 N for SDR, 35.8 N for Rebilda, and 14.7 N for cyanoacrylate, respectively. Both tested composites yielded significantly higher values in pull-out tests than cyanoacrylate. The disconnecting force was highest when light-cured composite SDR was used for fixation. Removing Hedstrom files resulted in higher values than removing K-files. The median force when using SDR was 79.7 N (interquartile range, 66.0-86.8 N) in Hedstrom files and 53.3 N (interquartile range, 47.1-58.5 N) in K-files.

Within the limitations of this study, the use of light-curing composite inside of the microtube was superior compared with the use of cyanoacrylate or chemically cured composite, which are being used presently.