This randomized, controlled, double-blinded clinical trial aims to directly compare the efficacy of Sonically Activated Irrigation (SAI) versus Passive Ultrasonic Irrigation (PUI) in the root canal treatment of teeth with chronic apical periodontitis, analyze potential influencing factors, and thereby identify a highly effective and safe root canal irrigation protocol. The ultimate goal is to provide an evidence-based rationale for optimizing irrigation technique selection and overall treatment strategies for chronic apical periodontitis.

Root canal therapy (RCT) is the common treatment for chronic apical periodontitis. Successful outcomes critically depend on the complete eradication of infection within the root canal system. The efficacy of infection control is significantly influenced by the irrigation technique employed. While passive ultrasonic irrigation (PUI) is a widely utilized form of activated irrigation in clinical practice, it carries inherent risks such as instrument separation and unnecessary dentin removal, limiting its use.

Sonically activated irrigation (SAI) represents a novel irrigation approach. Its polymeric tips circumvent the drawbacks associated with ultrasonic metal tips while delivering comparable irrigation efficiency. However, high-quality randomized controlled clinical evidence supporting its use is currently lacking.

This randomized, controlled, double-blinded clinical trial aims to directly compare the efficacy of SAI versus PUI in root canal treatment of teeth with chronic apical periodontitis and analyze potential influencing factors. The goal is to identify a highly effective and safe root canal irrigation protocol, ultimately providing an evidence-based rationale for optimizing irrigation technique selection and overall treatment strategies for chronic apical periodontitis.

Inclusion Criteria:

1. Agree to participate in this study and provide informed consent;
2. Age 18-59 years at the time of enrolment;
3. At least one permanent tooth diagnosed with chronic periapical periodontitis at root development stage of Nolla10th;
4. Able to follow up on schedule.

Exclusion Criteria:

1. Allergies to any medications or materials necessary to complete the procedures;
2. Non-restorable teeth, teeth with severe defects, or teeth that need to be extracted due to orthodontic treatment;
3. Teeth with root canal treatment or vital pulp therapy;
4. Teeth with canal calcification or root canal instrument separation;
5. Teeth with root fracture or vertical root fracture;
6. Tooth with internal or external root resorption;
7. Patients with periodontitis;
8. Patients with orthodontic treatment;
9. Presence of dental phobia;
10. Women who are pregnant;
11. Patients who have taken medications that affect central nervous system, such as tricyclic antidepressant;
12. Patients who have taken medications that affect immune response, such as glucocorticoid or cyclosporin;
13. Patients after radiotherapy of tumor head and neck;
14. Patients who have taken medications that affect curative effect, such as bisphosphonates;
15. Patients with serious systemic diseases that can affect curative effect;
16. Participation in other clinical studies within the past several weeks;
17. Patients who are deemed unsuitable to participate in the study by investigators.