All systems were associated with apical debris extrusion when canals were prepared to a large apical size. The PTU system was associated with more debris extrusion.

ObjectivesThis study evaluated the amount of remaining root canal filling materials after retreatment procedures performed by undergraduate students using manual, rotary, and reciprocating techniques through micro-computed tomographic analysis. The incidence of instrument fracture and the instrumentation time were also evaluated.Materials and MethodsThirty maxillary single rooted teeth were prepared with Reciproc R25 files and filled with gutta-percha and AH Plus sealer by the continuous wave of condensation technique. Then, the specimens were assigned to 3 groups (n = 10), according to the retreatment technique used: manual, rotary, and reciprocating groups, which used K-file, Mtwo retreatment file, and Reciproc file, respectively. Retreatments were performed by undergraduate students. The sample was scanned after root canal filling and retreatment procedures, and the images of the canals were examined to quantify the amount of remaining filling material. The incidence of instrument fracture and the instrumentation time were recorded.ResultsRemaining filling material was observed in all specimens regardless of the technique used. The mean volume of remaining material was significantly lower in the Reciproc group than in the manual K-file and Mtwo retreatment groups (p < 0.05). The time required to achieve a satisfactory removal of canal filling material and refinement was significantly lower in the Mtwo retreatment and Reciproc groups (p < 0.05) when compared to the manual K-file group. No instrument fracture was observed in any of the groups.ConclusionsReciproc was the most effective instrument in the removal of canal fillings after retreatments performed by undergraduate students.

Objective: this study evaluated the ability of rotary (ProTaper-Retreatment and Mtwo-Retreatment) and reciprocating (Reciproc and WaveOne) systems in maintaining the original shape of the canal after root canal retreatment. Material and Methods: forty curved resin blocks with simulated root canals were prepared and filled. After that, each block was randomly assigned to 4 groups (n = 10) according to the retreatment system used. Stereomicroscopic images from each block were taken before and after retreatment procedures. Evaluation of canal transportation was obtained for all canal length and for 2 independent canal regions: straight and curved parts. ANOVA followed by Tukey's test was used (P<0.05). Results: for all canal length ProTaper-Retreatment system showed lowest transportation values followed by Reciproc, MTwo-Retreatment and WaveOne systems (P <0.01). At the straight part, ProTaper-Retreatment system produced the lowest canal transportation followed by Reciproc and MTwo-Retreatment systems (P < 0.05); at the curved part, ProTaper-Retreatment and Reciproc systems produced the lowest canal transportation followed by MTwo-Retreatment system (P < 0.05). The WaveOne system resulted in the highest transportation values at both canal parts (P < 0.05). Conclusion: overall, ProTaper-Retreatment system produced less canal transportation in both portions of the simulated canals than the others systems tested after retreatment procedures.