Aim To determine the effect of blue thermal treatment on Reciproc (VDW, Munich, Germany) endodontic instruments and the amount of apically extruded debris during retreatment procedures. Methodology Thirty extracted mandibular molar teeth having mesial roots with a degree of curvature less than 20 degrees and having an initial apical size equivalent to a size 10 K-file were selected. The mesial roots of the teeth were removed from the cementoenamel junction to obtain a 15-mm root length. The mesiobuccal canals were prepared to size F2 using the ProTaper Universal system (Dentsply Sirona, Ballaigues, Switzerland), filled with gutta-percha and 2Seal (VDW) using the lateral compaction technique and then randomly divided into two groups (n = 15). The root fillings were removed with one of the following instruments using a crown-down preparation technique: M-Wire Reciproc or Reciproc Blue (both VDW). Apically extruded debris was collected in pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70 degrees C for five days to evaporate the distilled water. The data were analysed using the Mann-Whitney U test (P = 0.05). Results Reciproc Blue (1.42 +/- 0.4491 mg) extruded significantly less debris apically than M-Wire Reciproc (2.56 +/- 1.0232 mg) (P < 0.05). Conclusions Blue thermal treatment of Reciproc instruments was associated with less debris extrusion during retreatment procedures.