Effect of Low-level Laser Therapy Versus Calcium Hydroxide Intracanal Medication on Postoperative Pain and Substance P Levels in Patients With Symptomatic Apical Periodontitis

Inclusion Criteria: * Patients who are free from any physical or mental handicapping condition with no underlying systemic disease. * Age between 25-50 years old. * Males \& Females. * Single canaled teeth: * Diagnosed clinically with symptomatic apical periodontitis. * Widening in the periodontal membrane space or with small sized periapical radiolucency * Presence of pain with percussion and preoperative percussion pain level will be evaluated and recorded using modified visual analog scale (VAS). * Patients' acceptance to participate in the trial. * Patients who can understand pain scale and can sign the informed consent Exclusion Criteria: * Medically compromised patients: Pain levels and healing following treatment would be compromised as these patients have shown higher incidence of pain and lower healing rate. * Pregnant women: Avoid radiation exposure, anesthesia, and medication. * If analgesics or antibiotics have been administrated by the patient during the past 24 hours preoperatively might alter their pain perception. * Patients reporting bruxism or clenching: Avoid further pressure on an already inflamed tooth inducing subsequent irritation and inflammation. * Teeth that shows association with acute periapical abscess and swelling: Need special treatment steps which could involve additional visits with incision and drainage. Also, it could influence initiation and progression of postoperative pain. * Greater than grade I mobility or pocket depth greater…