Is to evaluate the influence of the calcium hydroxide / chlorhexidine combination and calcium hydroxide alone as an intra-canal medication in postoperative flare-up in two visits endodontic retreatment cases

Problem: patient needs retreatment Intervention: calcium hydroxide chlorhexidine combination as an intra-canal medicament Control: calcium hydroxide alone as an intra-canal medicament Outcome: postoperative flare-up (pain and swelling) Time: after 7 days from 1st visit. population will be examined:

1. Patients' needs retreatment.
2. Patients in good health with no systemic disease (American Society of Anesthesiologists Class II)
3. Age range is between 20 and 50 years.
4. Patients who can understand the categorical tool (points)for measurement
5. Patients able to sign informed consent.

Inclusion Criteria:

• 1. Patients' needs retreatment.
• 2. Patients in good health with no systemic disease (American Society of Anesthesiologists Class II)
• 3. Age range is between 20 and 50 years.
• 4. Patients who can understand the categorical tool (points)for measurement
• 5. Patients able to sign informed consent.

Exclusion Criteria:

• 1) Complicating systemic disease
• 2) Having severe pain and/or acute apical abscesses
• 3) Being under 18 years of age
• 4) Using antibiotics or corticosteroids,
• 5) having multiple teeth that required retreatment to eliminate the possibility of pain referral
• 6) Having root canals that could not be treated well with initial root canal treatment.