assess the effect of using reciprocating motion with reciproc files versus adaptive motion using twisted file adaptive on postoperative pain after instrumentation of necrotic mandibular molars.

In root canal treatment of mandibular molar teeth in patients having necrotic pulp with symptomatic or asymptomatic apical periodontitis, Is there difference in postoperative pain after instrumentation between two different kinematics; adaptive motion using Twisted File Adaptive and reciprocation motion using Reciproc

Inclusion Criteria:

1. Patients who are medically free from any systemic disease that may contraindicate our interventions.
2. Patient's age between 18-60 years old.
3. Mandibular molars having necrotic pulps with symptomatic or asymptomatic apical periodontitis because this group of patients may have more postoperative pain than vital teeth22.
4. Positive patient's acceptance for participation in the study.

Exclusion Criteria:

1. Patients who had used any type of analgesic medication during the preceding 12 hours before the treatment to give true response of pain after instrumentation.
2. Teeth with vital pulps or Symptomatic irreversible pulpitis.
3. Pregnant patients or lactating because of radiographic hazards and use of analgesics27.
4. Any known sensitivity or adverse reactions to ibuprofen.

participant data will be recorded and shared