This prospective randomized clinical study will investigate the association between MMP-2 and MMP-3 gene polymorphisms and radiographic healing outcomes following nonsurgical root canal treatment in patients with chronic apical periodontitis. A total of 50 patients will undergo standardized endodontic treatment and will be followed for 12 months. Genotyping will be performed using baseline DNA samples, and periapical healing will be assessed using the Periapical Index (PAI). The relationship between genetic variations and treatment outcomes will be analyzed to determine whether host-related genetic factors influence healing patterns after root canal therapy.

Inclusion Criteria:

• Single-rooted teeth
• PAI score ≥ 3
• Fully developed root apices
• Periodontal probing depth less than 5 mm
• Indication for primary nonsurgical root canal treatment

Exclusion Criteria:

• Previous endodontic treatment in the selected tooth
• Diagnosis of symptomatic apical abscess
• Presence of root fracture or internal/external resorption
• Use of systemic antibiotics within the previous 4 weeks
• Analgesic intake within 48 hours before treatment
• Ongoing immunosuppressive therapy
• Pregnancy or breastfeeding

The study population will consist of adult patients aged 18-65 years diagnosed with chronic apical periodontitis in single-rooted teeth and requiring primary nonsurgical root canal treatment. All participants will be classified as ASA I or II and will be recruited from patients referred to the Department of Endodontics. Only individuals meeting the predefined inclusion and exclusion criteria will be enrolled. Participants will undergo standardized treatment and follow-up under controlled clinical conditions.