This research will study the effect of NanoChitosan impregnated Calcium Hydroxide versus Calcium Hydroxide as an intracanal medication on postoperative pain intensity measured using numerical rating scale (NRS) and bacterial load reduction determined by bacterial counting using agar culture technique after root canal preparation (CFU/ml) in necrotic teeth.

Primary outcome: Postoperative pain measured using numerical rating scale (NRS)

1. After placement of intracanal medicament at 6, 12, 24 and 48 hours.
2. After root canal obturation at 6, 12, 24 and 48 hours.

Secondary outcome: Bacterial load reduction determined by bacterial counting using agar culture technique after root canal preparation (CFU/ml)

1. Sample 1 (S1): after access preparation and pre-instrumentation.
2. Sample 2 (S2): post-instrumentation.
3. Sample 3 (S3): post-intracanal medicament removal at 7 days.

Inclusion Criteria:

1. Age between 25-45 years old.
2. Males or females.
3. Healthy patients who are categorized as I or II according to The American Society of Anesthesiologists. (ASA I or II)
4. Patients' accepting to participate in the trial.
5. Patients who can understand the pain scale and can sign the informed consent.
6. Mandibular Single rooted premolars, having single root canal: Diagnosed clinically with pulp necrosis.
7. Positive pain on percussion denoting apical periodontitis.(20)
8. Slight widening in the periodontal membrane space
9. Normal occlusal contact with opposing teeth

Exclusion Criteria:

1. Medically compromised patients having significant systemic disorders (ASA III or IV).

2. If analgesics or antibiotics have been administrated by the patient during the past 24 hours preoperatively.

3. Pregnant women

4. Patients reporting bruxism, clenching, TMJ problems or traumatic occlusion

5. Patients with two or more adjacent teeth requiring endodontic treatment.

6. Teeth that require further procedural steps or multidisciplinary approach.

   1. Association with swelling or fistulous tract.
   2. Acute periapical abscess.
   3. Mobility Grade II or III.
   4. Pocket depth more than 5mm.
   5. Previous root canal treatment.
   6. Non-restorable.
   7. Immature root.
   8. Radiographic evidence of external or internal root resorption, vertical root fracture, perforation, calcification.

7. Inability to perceive the given instructions.

Outcome assessors (patients and statistician) will not know which group the participants are related to