A laboratory study comparing two methods for removing plastic carrier obturators from severely curved root canals

Removing plastic carrier obturators during root canal retreatment is challenging and often takes a long time. The aim of this laboratory investigation is to compare a recently described indirect, two-stage technique for removing plastic carriers from curved canals and evaluate its efficiency, safety and efficacy in comparison to a conventional direct technique.

Thirty-six extracted mandibular premolars were chosen and root filled with plastic carrier obturators and endodontic cement. The teeth were allocated randomly into two different retreatment techniques: Group 0 (Direct technique), where the plastic carriers were removed together with the gutta-percha using rotary NiTi files; Group 1 (Indirect technique), where the carriers were removed first using an ultrasonic tip and Hedström files, with the surrounding gutta-percha being removed subsequently with rotary NiTi endodontic files. The duration of retreatment procedures, number of fractured instruments and plastic carriers, ledge formation, apical transportation and root canal perforations were recorded for each technique, as well as the amount of remaining root filling material. The Student's t-test and Fisher's exact tests were used to determine significant differences among groups for each variable.

Removal of root fillings was significantly more rapid in Group 1 (p < 0.05). Fracture of the carrier, ledge creation and apical deviation, occurred significantly less often in Group 1 (p < 0.05), although the intergroup comparisons of the other variables revealed no significance differences (p > 0.05). Root canal perforations did not occur in either group.

In this laboratory study on extracted teeth, the indirect technique of removing plastic carriers before the gutta-percha was more rapid and associated with fewer intra-operative complications in terms of fracture of the carrier, ledge formation and apical transportation.