Evaluation of various filling techniques in distal canals of mandibular molars instrumented with different single-file nickel-titanium systems

The aim of this study was to evaluate the quality of various filling techniques in distal canals of mandibular molars instrumented with different single-file nickel-titanium (NiTi) systems. A total of 150 distal roots of mandibular molar teeth were randomly assigned into three main groups and instrumented by using Reciproc (VDW, Munich, Germany), WaveOne (Dentsply Tulsa, Tulsa, OK, USA), or One Shape (MicroMega, Besancon, France) NiTi file systems. The roots were then treated using one of five filling techniques: (1) Matched-single-cone, (2) cold lateral compaction with matched gutta-percha (GP) cone, (3) Thermafil filling, (4) System B/Obtura II, and (5) lateral compaction with standardized GP cones. The roots were then sectioned at three levels (coronal, middle, and apical). Photographs were acquired under a stereomicroscope, and the percentage of GP-filled areas (PGFAs), percentage of sealer-filled areas (PSFAs), and voids were measured using the ImageJ software. Comparisons between groups were applied using Student's t-test or one-way ANOVA for normally distributed data. The Mann-Whitney U-test or Kruskal-Wallis test was used when variables were not normally distributed. Canals filled with the System B/Obtura showed the highest PGFA and lowest PSFA, whereas those filled with matched-single-cone showed the highest PSFA and lowest PGFA (P < 0.05). The cold lateral compaction with matched GP cone group, lateral compaction group, and Thermafil filling group showed no statistically significant differences in PSFA and PGFA (P > 0.05). System B/Obtura technique appears to be the best technique to properly fill root canals, whereas the matched-single-cone technique in oval-shaped distal canals of mandibular molars was inadequate.