The aim of this study is to evaluate in vivo the post operative pain after laser root canal treatment in necrotic teeth in an evidence-based clinical trial. The null hypothesis being tested is that there is no difference in post operative pain between conventional irrigation and the two types of lasers used.

Forty-five patients are equally divided into 3 separate groups :

• Group A (Conventional): 2.5% NaOCL and 17% EDTA.
• Group B(Dual): saline along with Er,Cr:YSGG laser and diode laser combination
• Group C(Combined): saline along with 17% EDTA and diode laser combination Each patient is given pain scale chart Numeric Rating Scale (NRS) to record his/her pain level before any endodontic treatment. All data will be collected, tabulated, summarized, and statistically analyzed.

Postoperative pain is a common complication following conventional endodontic treatment. According to a systematic review, the frequency of endodontic postoperative pain is between 3% and 58% of patients.Postoperative pain is attributed to chemical, mechanical and microbiological factors.

Residual microorganisms remaining due to the complexity of the root canal system and the limited penetration capability of conventional irrigants are directly responsible for Post operative pain The aim of this study is to evaluate in vivo the post operative pain after laser root canal treatment in necrotic teeth in an evidence-based clinical trial. The null hypothesis being tested is that there is no difference in post operative pain between conventional irrigation and the two types of lasers used.

Forty-five patients are equally divided into 3 separate groups :

• Group A (Conventional): 2.5% NaOCL and 17% EDTA.
• Group B(Dual): saline along with Er,Cr:YSGG laser and diode laser combination
• Group C(Combined): saline along with 17% EDTA and diode laser combination Each patient will be given pain scale chart (NRS scale) to record his/her pain level before any endodontic treatment. After disinfection, local anesthetic, tooth isolation, access cavity preparation and final obturation. Patients are asked to mark on a numeric rating scale (NRS) to determine incidence of postoperative pain and rate its intensity at 6, 12, 24, 48, 72 hours, and 7 days after the procedure All data will be collected, tabulated, summarized, and statistically analyzed.

Inclusion Criteria:

• Patients who had asymptomatic, single-rooted maxillary anterior teeth with necrotic pulp and periapical lesion with a periapical index score of 3 or 4
• Patients complaining of no pain and without fistulous tract
• Closed apex.
• Acceptance to participate in the study.

Exclusion Criteria:

• Antibiotic use within the last month, anti-inflammatory analgesic use within the last 5 d, systemic diseases or allergic reactions, calcified canals, root resorption, previous root canal treatment.
• Periodontal diseases, presence of swelling or fistulous tract.
• Vulnerable group including pregnant females, mentally or physically disabled individuals. - Technical difficulties during root canal treatment such as; curved roots, broken files, over instrumentation, overfilling or incomplete filling.