The goal of this clinical trial is to evaluate the expression of inflammatory mediators in the crevicular fluid and periodontal ligament after one-visit root canal treatment of mandibular molars of patients with asymptomatic irreversible pulpitis using 3 different file systems.

The main question it aims to answer is: Does conservative root canal preparation cause decreased expression of inflammatory mediators compared to conventional root canal preparation?

In this context, patients will be divided into 3 groups based on the file systems as follows: ProTaper Gold, OneShape, and TruNatomy up to apical size #25. Both inflammatory mediator expression and postoperative VAS values will be compared.

The below-mentioned steps will be performed in the scope of this study:

1. Ethical approval has been obtained.
2. The sample size calculation was performed (90% power, 0.597 effect size, 20 patients per group)
3. Patients aged 18-60 with asymptomatic irreversible pulpitis that has been confirmed by intraoral and extraoral examination and without any systemic disease will be included.
4. Only mandibular first and second molar teeth that do not have complex anatomy, periapical lesions, deep periodontal pockets (PAI<2), and any fractures or cracks will be included.
5. Patients with acute symptoms, a history of taking analgesics 48 hours or antibiotics within 1 month prior to the visit, being pregnant and lactating, and having several periodontal problems will be excluded.

5) Immature apexes and trauma cases will also be excluded. 6) Selected patients will be informed about the study, and written consent will be obtained from all patients.

7) Patients will be randomly distributed into groups using a software (www.randomizer.org). Moreover, patients will be blinded regarding the file system they use.

8) A single operator will perform all endodontic treatments in the same clinical conditions.

9) Before starting the treatment, the baseline Visual Analogue Scale (VAS) values will be recorded.

10) For baseline inflammatory mediator assessment, gingival crevicular fluid samples from mesial and distal surfaces from teeth with #20 paper points for 30 seconds and paper points will be placed into Eppendorf tubes and kept at -80 ° until the analysis is performed.

11) After the administration of the local anaesthesia, teeth will be isolated with a rubber dam, and access cavities will be prepared. Then, teeth will be allotted to one of the following file systems:

• Group 1 (ProTaper Gold file system): Sx-S1-S2-F1-F2 (for mesial canals), F3 (for distal canal)

• Group 2 (OneShape file system): 25/.06 (for mesial canals), additional file for distal canal if needed.

• Group 3 (TruNatomy file system): 17/.02, 20/.04 ve 26/.04 (for mesial canals), 36/.03 (for distal canal.)

  12) 2 mL 2.5% sodium hypochlorite (NaOCl) will be used between files and final irrigation will be performed using 5 mL NaOCL, 5 mL 17% ethylenediaminetetraacetic acid (EDTA), and 5 mL distilled water with 31-G side vented needle.

  13) After drying the canals, #15 paper point will be placed inside mesial canals for 1 minute, 2 mm beyond the apex. Afterwards, paper points will be placed into Eppendorf tubes and kept at -80 ° until the analysis is performed.

  14) Root canals will be obturated with resin-based sealer and gutta-percha. 15) Permanent restoration will be done using composite. 16) Patients will be recalled at 24 and 72 hours, and gingival crevicular fluid samples from mesial and distal surfaces will be obtained using an above-mentioned method.

  17) Measurement of postoperative pain after treatment with a VAS scale at 24, 48, and 72 hours will also be recorded.

  18) Measurement of pain mediators (Substance P, Prostaglandin E2, interleukin (IL) 6, and IL-10) will be performed with ELISA kits. All samples will be analyzed in duplicate.

  19) Based on the readings obtained from the spectrophotometer, results will be fitted to the standard curve and presented in the form of picograms per millilitre (pg/mL).

  20) Statistical analysis will be conducted.

Inclusion Criteria:

• Patients aged 18-60
• Patients with asymptomatic irreversible pulpitis that has been confirmed by intraoral and extraoral examination
• Patients with pain pain between 0 and 3 on the VAS scale
• Patients without any systemic disease
• Mandibular first and second molar teeth without complex root canal anatomy, calcifications, periapical lesions, deep periodontal pockets (PAI<2), and any fractures or cracks

Exclusion Criteria:

• Patients with acute symptoms
• Patients who have a history of taking analgesics 48 h or antibiotics within 1 month prior to the visit
• Patients who are being pregnant and lactating
• Patients with several periodontal problems
• Patients with systemic disease
• Teeth with immature root apexes
• Trauma cases

Within the scope of the necessity of protecting the individual information of the patients, it is considered that the recorded data will not be shared.

Patients who will be treated and the assessor who will perform the analysis in lab will be blinded regarding which file is used for each patient.