The goal of this clinical trial is to primary purpose investigate and compare oxidative stress markers in patients with chronic apical periodontitis treated with different root canal paste in a single session. The main questions it aims to answer are:

Is there a change in oxidative stress markers measured from saliva after root canal treatment? Is there a difference between the change of oxidative stress markers in patients using different root canal sealers after root canal treatment?

Researchers will compare bioceramic-based and epoxy resin-based root canal sealers to see if there are significant differences in oxidative stress markers measured from patients' saliva after root canal treatment.

• Participants will be informed about all procedures before starting the clinical process.
• Participants are expected to allow saliva sampling two times: first sample will be collected on root canal treatment session and second sample will be collected on the 30th day after root canal treatment.
• Participants will be informed in writing about the treatment procedure before starting the clinical process.
• Participants are expected to sign the informed consent form on a voluntary basis.

Inclusion Criteria:

• Systemically healthy, ASA1 patients,
• Phase 1 periodontal treatment was performed,
• Diagnosed with chronic apical periodontitis in a single tooth with 2 or more roots in the mouth,
• The lesion measured <2 cm on radiographic evaluation,
• The vitality of the tooth was checked by EPT (Ai-Pex, Woodpecker, China) and Cold test (Cerkamed, Poland) and confirmed to be devitalised,
• Socioculturally able to participate in the treatment,
• Individuals who did not smoke or drink alcohol

Exclusion Criteria:

• Patients who have used antibiotics in the last three months and analgesics in the last two weeks
• Patients who smoke and/or abuse alcohol
• Patients younger than 18 years or older than 45 years,
• Patients with controlled or uncontrolled systemic disease and life-threatening conditions (ASA 2,3,4,5,6)
• Pregnant or lactating women,
• Patients with poor oral hygiene,
• Patients who had head and neck radiotherapy,
• With obesity,
• Active periodontal disease,
• Periodontal pocket depth over 3mm,
• There is enough loss of material in the relevant tooth to prevent adequate isolation or to require post placement,
• Clinical examination of the relevant tooth showing symptoms in percussion-palpation,
• Radiographically, the lesion is seen in relation to anatomical formations such as the mandibular canal and maxillary sinus,
• Patients who required prophylactic antibiotic use before invasive dental procedures were excluded from the study.
• Patients who did not attend the follow-up appointment and patients who experienced complications during expansion (instrument seperation, perforation, etc.) were excluded from the study.

The root canal paste to be used will be selected from identical black envelopes by another physician who will not participate in the treatment.