This study will compare the outcome of single visit retreatment and multi-visit retreatment in cases of failed root canal treated teeth.

Retreatment is defined as a procedure to remove root canal filling materials from the tooth, followed by cleaning, shaping and obturating the canals.Although initial root canal therapy has been shown to be a predictable procedure with a high degree of success, failures can occur after treatment. Recent publications have reported failure rates of 14%-16% for initial root canal treatment. In order to prevent tooth loss in such cases, nonsurgical retreatment or apical surgery is often indicated.

In this study subjects will be assigned to either the single-visit and multi-visit nonsurgical endodontic retreatment. The allocation will be performed once the chemomechanical preparation is completed.

Clinical and radiographic success rate will be considered as primary outcome. Follow up will be carried out every 3 months, till 12-month period.

Pain intensity will be considered as secondary outcome.

Inclusion Criteria:

• Patient willingness to participate in the study.
• Previously root filled Permanent teeth with post-treatment apical periodontitis requiring nonsurgical root canal retreatment.
• Failure of previous root canal treatment will be determined based on clinical and radiographic findings. Clinical indicators of failure will include pain, tenderness to palpation/percussion, swelling, sinus tract.Radiographic criteria will include persistent periapical radiolucent lesions in teeth in which initial treatments were performed at least 4 years previously.
• Root canal fillings no more than 4mm short of the apex.
• Patients showing no significant systemic disease

Exclusion Criteria:

• Patients who are pregnant, diabetic, immunocompromised, serious medical illness or requiring antibiotic premedication.
• Patient under 18 years of age.
• Patient under corticosteroid use.
• Patients with history of antibiotic use in last 3 months or analgesic use in last one week will also be excluded.
• Multiple teeth that require treatment to eliminate the possibility of pain referral.Patients with unrestorable carious lesions, fractures involving the periodontium, and/or periodontal pockets ≥ 4mm deep or having marginal or furcal bone loss due to periodontitis .
• Teeth with the procedural errors preventing access to apical third and missed canals will be excluded.
• Teeth that are not suitable for rubber dam isolation.
• Teeth with intraradicular post.