The goal of this observational study is to define the role of apical shaping and irrigation activation on root canal cleanliness. The main questions it aims to answer are:

• does the effectiveness of irrigation activation depends on apical shaping?
• can a similar success be achieved by increasing apical shaping without irrigation activation Participants will [describe the main tasks participants will be asked to do, treatments they'll be given and use bullets if it is more than 2 items].

The aim of this study is to evaluate the effect of apical enlargement with two different diameters on the intraradicular microbiota of teeth with chronic apical periodontitis lesion before and after passive ultrasonic irrigation activation using ddPCR analysis in vivo.The study was planned as a randomized controlled clinical trial. We are planning to include 24 patients who was referred to the Istanbul Medipol University Faculty of Dentistry Endodontic Clinic with the need for root canal treatment, with asymptomatic chronic apical periodontitis. 24 patients will randomly be assigned to two groups according to the apical shaping size during root canal treatment: 25/.04 and 35/.04. Microbiological sampling of the teeth will be done with paper cones in three steps during the root canal treatment: 1. Sterility control samples (SR1) from the tooth surface after cavity preparation, 2. The first microbiological sample (S1) from the root canal after the initial file reaches the working length. 3. The second microbiological sample (S2) from the root canal after the shaping and irrigation of the root canal is finished. 4. The third microbiological sample (S3) from the root canal after the irrigation activation in the root canal is finished.The samples will be sent to the genetic analysis laboratory for further analysis in the cold chain using a Droplet Digital PCR.

Inclusion Criteria:

• Patients between the ages of 18-65
• Patients complying with the ASA1 and ASA2 classification (American Society of Anesthesiology)
• Patients who has molar teeth with radiolucent lesions in the periapical region
• The volunteer himself/herself or his/her legal representative wants to participate in the research by signing the 'Voluntary Consent Form'.
• Being able to tolerate the treatment physically and mentally

Exclusion Criteria:

• Patients who have taken antibiotics/corticosteroids in the last 3 months
• Patients with systemic disease
• Teeth that cannot be properly isolated with a rubber dam
• Teeth without coronal sealing,
• Teeth with periodontal pocket depth>4 mm and teeth with crown / root fracture.
• Individuals who continue or are considering starting orthodontic treatment during the research
• Pregnant and lactating individuals
• The volunteer himself/herself or his/her legal representative does not want to participate in the research by signing the 'Voluntary Consent Form'.
• Teeth that are damaged enough to require post-core treatment.

24 patients who was referred to the Istanbul Medipol University Faculty of Dentistry Endodontic Clinic with the need for root canal treatment, with asymptomatic chronic apical periodontitis, witj clinical and radiographic findings. The study will be carried out in Istanbul Medipol University Faculty of Dentistry Endodontic Clinic, and patients with appropriate criteria will be informed about the treatment to be performed and their consent will be obtained. In this observational type study, patients treated by the same physician will be followed.

due to regulatory reasons the participant data will not be shared.