This clinical study will compare different root canal disinfection methods used during primary root canal treatment. Root canal infection is mainly caused by bacteria inside the root canal system. Sodium hypochlorite is commonly used as a root canal irrigant because it helps reduce bacteria. Photodynamic therapy is an additional disinfection method that uses a photosensitizing solution and light activation to help kill bacteria. Participants who need primary root canal treatment will be randomly assigned to one of the study groups. The study will compare sodium hypochlorite irrigation alone with sodium hypochlorite supplemented with photodynamic therapy. Additional comparison groups will be used to assess the antimicrobial effect of the disinfection procedures. Bacterial samples will be collected from the root canals before and after the assigned disinfection protocol to measure the reduction in bacterial counts. The main outcome of the study is the reduction in intracanal bacterial load after the disinfection procedure. Postoperative pain will also be assessed using a visual analogue scale at selected time points after treatment. All participants will receive standard root canal treatment, and the final clinical disinfection and treatment procedures will be completed according to accepted endodontic practice.

This is an in vivo randomized clinical study designed to evaluate the antimicrobial effect of root canal disinfection protocols during primary root canal treatment. The study focuses on the reduction of viable intracanal bacteria following irrigation with sodium hypochlorite, with or without adjunctive photodynamic therapy. Eligible participants requiring primary root canal treatment will be enrolled and randomly allocated to one of the study groups according to the approved protocol. Under rubber dam isolation, root canal treatment will be performed using standard endodontic procedures. Intracanal microbiological samples will be collected using sterile paper points before and after the assigned disinfection protocol. The collected samples will be processed for culture-based microbiological analysis, and bacterial reduction will be assessed by comparing viable bacterial counts before and after the intervention. Photodynamic therapy will be used as an adjunctive disinfection method in the relevant study group. This technique involves the use of a photosensitizing agent followed by activation with light of an appropriate wavelength to produce an antimicrobial effect. Sodium hypochlorite irrigation will be used as the standard chemical disinfection method. For ethical and clinical safety reasons, all participants will receive completion of treatment according to accepted endodontic standards. Postoperative pain will be recorded after treatment using a visual analogue scale. The study is intended to determine whether adding photodynamic therapy to sodium hypochlorite improves intracanal bacterial reduction compared with sodium hypochlorite irrigation alone during primary root canal treatment.

Inclusion Criteria:

• Patients aged 18 to 70 years.
• Medically healthy patients or patients with well-controlled systemic conditions, such as controlled diabetes or controlled hypertension.
• Patients requiring primary root canal treatment in mature, single-rooted, single-canal teeth.
• Teeth with a confirmed diagnosis of pulp necrosis, with or without apical periodontitis.
• Teeth that are restorable.
• Teeth suitable for single-visit root canal treatment.
• Teeth suitable for rubber dam isolation.
• Cases with dry canals that do not require inter-appointment medication.
• Participants who provide written informed consent before treatment.

Exclusion Criteria:

• Patients with uncontrolled systemic disease.
• Patients with immunocompromised status.
• Patients with any condition that could affect infection, healing, or treatment response.
• Patients who used systemic antibiotics within the previous three months.
• Patients who used analgesic or anti-inflammatory medication shortly before treatment.
• Pregnant or lactating patients.
• Patients with known allergy or contraindication to any study material.
• Teeth with irreversible pulpitis.
• Teeth with previous root canal treatment or retreatment indication.
• Teeth with immature apices.
• Teeth with internal or external root resorption.
• Teeth with cracks, fractures, or perforations.
• Teeth with unusual canal anatomy that could prevent procedural standardization.
• Teeth with advanced periodontal involvement.
• Teeth with unrestorable coronal structure.
• Canals with persistent exudate.
• Cases with acute swelling or acute abscess.
• Any condition requiring multi-visit treatment.

Individual participant data will not be shared. Only aggregated and analyzed study results may be reported in the thesis, scientific presentations, or publications.