A hundred twenty patients who had an asymptomatic mandibular molar teeth with periapical lesion were included. For each patient, teeth were prepared with Reciproc Blue or Protaper Universal instruments. Each tooth was obturated with gutta-percha and resin-based sealer using single cone technique for mesial roots and for distal roots single cone and cold lateral compaction technique. Root canal treatment was performed in a single visit. Postoperative pain was assessed as no, mild, moderate, or severe at 6, 12, 24, 48, 72 hours and 7 days after obturation.

The aim of this study was to compare the effect of root canal preparation techniques on the occurrence and intensity of postoperative pain in patients with asymptomatic mandibular molar teeth with periapical lesions.A hundred twenty patients who had an asymptomatic mandibular molar teeth with periapical lesion were included. For each patient, teeth were prepared with Reciproc Blue or Protaper Universal instruments. Each tooth was obturated with gutta-percha and resin-based sealer using single cone technique for mesial roots and for distal roots single cone and cold lateral compaction technique. Root canal treatment was performed in a single visit. Postoperative pain was assessed as no, mild, moderate, or severe at 6, 12, 24, 48, 72 hours and 7 days after obturation.For the comparison of pain scores between the tested instrumentation systems, the Mann Whitney test was used. Differences between postoperative pain intencity for each instrumentation technique, at different time intervals, were assessed by the Friedman test. For the association of pain and an analgesic intake with gender, the chi-square test was performed. For the association of pain with age and an analgesic intake were calculated using Mann Whitney test. A P value < .05 or less was considered significant.

Inclusion Criteria:

• Patients without systemic diseases
• Patients who had a mandibular first molar with asymptomatic periapical lesion without previous endodontic treatment with no sensitivity to percussion
• Patients who had no spontaneous pre-treatment pain
• Patients not having taken any analgesics, antibiotics or corticosteroids before the treatment visit,
• Patients who had no allergic reaction to NaOCl and no intolerance to nonsteroidal anti-inflammatory drugs.

Exclusion Criteria:

• Patients who had severe periodontal disease
• The teeth with previous endodontic treatment
• The teeth with root canal calcification, root resorption
• The teeth that could not be isolated with rubber dam or were not suitable for further restoration