The goal of this clinical trial is to learn which of three common root-canal rinsing (irrigation) methods removes bacteria most effectively in adult patients who need root-canal treatment. The main questions it will answer are:

How much does a chitosan solution used alone lower the number of bacteria inside the root canal? Do the combinations sodium hypochlorite + chitosan or sodium hypochlorite + EDTA lower bacteria even more than chitosan alone? Researchers will compare the three irrigation methods to see which one achieves the greatest bacterial reduction.

What participants will do

Be randomly assigned to one of three groups:

Group 1: Chitosan only Group 2: Sodium hypochlorite followed by chitosan Group 3: Sodium hypochlorite followed by EDTA

Attend two clinic visits:

Visit 1:

Receive standard root-canal treatment under local anesthesia. Provide tiny paper-point samples from inside the canal before and after the assigned rinse (painless; takes seconds).

Visit 2 (about 1 week later):

Return for a check-up and final filling of the tooth. Record any pain or discomfort for the first three days after treatment in a simple diary (or by phone).

About 90 adults will take part. All procedures are routine in dental care, and there is no cost to participate. Participants may withdraw at any time and can ask the study dentist any questions throughout the trial.

Inclusion Criteria:

• Patients who agreed to participate in the study
• Systemically healthy patient
• Mandibular premolar teeth
• Teeth that respond negatively to thermal tests and EPT
• Patients who have not used antibiotics for at least 2 weeks

Exclusion Criteria:

• Teeth with previous primary root-canal treatment
• Pregnant patients
• Severely curved roots (>25° curvature)
• Canals with instrument separation during preparation
• Calcified (obliterated) canals

De-identified participant-level log10 CFU/mL data (baseline and immediate post-instrumentation) will be available 12 months after publication. Researchers may request the dataset by emailing the Principal Investigator; a data-sharing agreement will be required.

Beginning 12 months after primary publication and ending 5 years after publication

Access to the de-identified participant-level log10 CFU/mL dataset (baseline and immediate post-instrumentation) will be granted to qualified, non-commercial academic investigators.

Requests must include a brief research proposal and proof of institutional ethics approval, and should be e-mailed to the Principal Investigator (dagci.esra.496@gmail.com). After approval and signature of a data-sharing agreement that prohibits re-identification or further redistribution, the dataset and data dictionary will be transferred via a secure, password-protected file-sharing service.

No clinical charts, radiographs, consent forms, or ethics-committee documents will be shared. Data will be available beginning 12 months after primary publication, with no end date.