The aim of the study is to evaluate the effect of piroxicam (20mg) compared to placebo on post-endodontic pain of single-visit endodontic treatment of non-vital mandibular molars.

• Patients will be clinically and radiographically examined and their eligibility will be assessed. Eligible patients will be treated in one visit.
• Patients will be randomly assigned to one of 2 groups: experimental group (premedication with 20 mg of piroxicam) and the control group (premedication with placebo). Each participant will receive a standard inferior alveolar nerve block injection. After endodontic treatment, patients will be given postoperative instructions and informed, in case of pain, to receive ibuprofen 200 mg as rescue medication.
• Postendodontic pain intensity and incidence at the different pain categories (No, mild, moderate, severe) will be assessed 6, 12, 24, 48, 72 hours and 7 days postoperatively using a 0-10 numerical rate scale (NRS). Analgesic intake throughout the 7 days will be recorded.

Inclusion Criteria:

1. Patients aging between 18-50 years old
2. Patients with mandibular molar with non-vital pulp.
3. Systemically- healthy patients (ASA I or II).
4. Patients who agree to attend for recall appointments and provide a written consent.

Exclusion Criteria:

1. Pregnant or lactating female patients.
2. Patients allergic to piroxicam.
3. History of peptic ulceration.
4. Periapical abscess, fistula.
5. Non-restorable teeth.
6. Moderate or severe marginal periodontitis i.e. pocket probe>3mm.

The study will be participant and operator-blind where the participant and operator will not know the intervention done.