The goal of this clinical trial is to learn if using bioceramic sealers in non surgical single visit endodontic retreatment in patients with endodontic treatment failure and asymptomatic apical periodontitis will work in comparison to other resin sealer which proved efficacy ,and help healing of the periapical lesions and reduce the anticipated postoperative pain , Participants will have root canal retreatment done in a single visit and then follow up will be done in 1, 3 and 6 months to check healing and then after 12 months , also postoperative pain will be monitored through communicating the patients after 24, 28 , 72 hours and the 7 days

selection of the cases will be done according to the eligibility criteria the a baseline periapical radiograph to record the periapical index and base line CBCT will be done to measure the lesion size and record the CBCTPAI then patients will be divided into two groups (A AND B) randomly to perform single visit non surgical root canal retreatment using bioceramic sealer in obturation in group A and resin sealer in group B then post operative pain assessment will be done using numerical scale after 24, 48, 72 hours and 7 days .for radiographical and clinical measuring of the healing follow up will done after 1, 3, 6 and 12 months by performing periapical radiographs and recording PAI and clinical signs or symptoms and CBCT after 12 months to record CBCTPAI and compare the size differences at baseline

Inclusion Criteria:

1. Mandibular molar teeth with previous unsuccessful endodontic treatment from ≥ 1 year with asymptomatic apical periodontitis.

2. Teeth with inadequate obturation.

3. Teeth with broken instruments that can be bypassed and/or retrieved and not present in the apical third or passing through the apex.

4. Teeth with periapical lesion.

5. Patient with the ages of 18-65 years.

6. Patient medically healthy and free from systemic diseases or with mild controlled systemic disease. ASA I, II * (52).

7. Patient with no acute pain or extraoral swelling.

8. Patients who agreed to participate in the study and attend the control visits.

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Exclusion Criteria:

1. Teeth requiring retreatment with a poor prognosis (root canal morphology altered, large carious cavity, internal or external root resorption, root perforation)

2. Teeth with vertical root fracture or open apex.

3. Patient with systemic disorders related to bone metabolism and using drugs that may affect bone metabolism.

4. Pregnant patients.

5. Patient under antibiotics treatment 2 weeks before the treatment.

6. Patients who could not attend follow up will be excluded from the study

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study design and statistical analysis

from January 2025 with no end date

study protocol and other data relative to the study is available at Alexandria university faculty of dentistry official site , can be accessed by anyone who would ask for