Chemomechanical preparation of the root canal system potentially results in extrusion of debris into the periradicular tissues. This debris is composed of hard tissue (dentin), soft tissue (inflamed or necrotic pulp tissues) and microbiota. Furthermore, the chemical adjuncts used during root canal disinfection may also extrude into the periradicular tissues. Extrusion of such materials results in postoperative pain, inflammation and and flare-up. There is evidence to demonstrate that most instrumentation techniques cause extrusion of debris, and that, severity of the inflammatory response depends on the amount of debris extrusion. Several factors may influence the debris extrusion during root canal preparation, including the instrument design, technique of use and irrigating agent used during preparation.Sodium hypochlorite (NaOCl) is the most commonly used root canal irrigant during root canal treatment. However, its cytotoxic effects when extruded into the periapical tissues is an issue of clinical concern. Thus, there has been a search for more biocompatible irrigants. One potential option, which has not been explored in detail, is the use of NaOCl, but in a gel form rather than a solution. NaOCl gel has similar effects on the dentin, as the solution form. Interestingly, greater dentinal tubule penetration depth has been reported for the gel form, compared to the solution. Previous studies have evaluated the effect of preparation techniques, the number of appointments and intracranial medicaments on postoperative pain during Endodontics treatment. There is no study evaluating the effect of different irritant type on PP. Therefore, this study will be evaluated the effect of different irritant type (gel or solution form of NaOCI) on postoperative pain.

1. The study is planned to be performed on 104 patients who are aged between 18-45 years and who have no systemic disease and are diagnosed and followed up in Yüzüncü Yıl University Faculty of Dentistry, Department of Endodontics.

2. Patients who have been diagnosed with irreversible pulpitis will be included in the study group.

3. Patients with periapical lesions and incomplete apex development will not be included in the study group.

4. The access cavity will be prepared under local anesthesia.Working length of the canal will be determined as it ends in apical constriction, by using 15 k file with apex locater and periapical radiographs.

5. Preperation of root canals will be finished with ProTaperNext X3 instrument as standard and applied to each patient.

6. All patients will be randomly divided into two groups according to the irrigation protocol (G1: 5.25% NaOCI; G2: Chloraxid gel / distilled water) (n = 250).

7. Group 1: 2 ml of 5.25% NaOCl solution will be used as irrigation solution at every file change during root canal preperation .2 ml dental injector and 27 gauge thickness dental needle tip will be used for irrigation . The tip of the cannula will be adjusted to reach two-thirds of the working length.

   Group 1: 2 ml of 5.25% Cloraxid gel/ distilled water will be used as irrigation solution at every file change during root canal preperation .2 ml dental injector and 27 gauge thickness dental needle tip will be used for irrigation. The tip of the cannula will be adjusted to reach two-thirds of the working length.

8. Final irrigation procedure after canal preperation, 5 ml of 5.25% NaOCl solution, 5 ml of 17% EDTA solution, 5.25% NaOCl solution will be used respectively for both groups as standard.

9. After the final irrigation process, the root canals will be dried with sterile paper points, then they will be filled with sterile gutta-percha with lateral condensation technique by hand spredars. After root canal filling teeth will be restorated for coronal sealing.

10. After the treatment, the patients in both groups will be asked to report the pain levels at certain intervals (6th hour-24th hour-48th hour-72th hour-1st week) according to the VAS scale.

11. According to the questionnaires collected with patient feedbacks, the data will be analyzed and interpreted with statistical analysis ** (manwithney u-kruskall Wallis) in order to evaluate the pain levels after single visit root canal treatment.

Inclusion Criteria:

• Healthy persons between the ages of 18 and 45 years
• Mandibular molar teeth that were diagnosed with symptomatic irreversible pulpitis

Exclusion Criteria:

• Patients who are taken analgesic inflammatory drugs with in the last 12 hours
• Pregnancy or lactation
• Teeth with calcified canals
• Teeth with periodontal diseases
• Teeth with sensitive to percussion and palpation
• Teeth with root resorption
• Teeth with immature/open apex