Influence of Calcium hydroxide Chlorhexidine Combination vs. Calcium Hydroxide as an Intra canal Medicamentson Postoperative flare -up following two-Visit Endodontic Retreatment cases

1. Each patient will be anesthetized with the same solution, 40 mg articaine hydrochloride + 0.006 mg/mL epinephrine hydrochloride (Ultracaine DS; Aventis Pharma, Istanbul, Turkey).

2. The standard procedure for each group at the first appointment included rubber dam isolation,removing of previous coronal restorations, and root canal filling materials. The removal of previous root canal fillings will be performed with one of these: Gates Glidden drills, hand files, heated pluggers, and Ni-Ti rotary instruments.

3. After the removal of previous root canal fillings, the working lengths were determined by apex locator and periapical radiographs 1 mm from the apexes.

4. Chemo-mechanical preparation of root canals will be made with the master apical files ranged from #25 to #70 depending on the initial diameter or preparation of the root canals.

   Irrigation was performed with 2.5% NaOCl after each instrument in all cases. At the end of instrumentation, the final irrigation was made by saline, and the root canals were dried with paper points.

5. In the 1st group the root canals will be medicated with a calcium hydroxide paste for 7 days.(calcium hydroxide injectable paste Metapex , 2.2g paste in a 1 syringe).

   In the 2nd group the root canals will be medicated with a calcium hydroxidechlorhexidine paste for 7 days. The paste consists of 1.2 g Ca(OH)2 powder per 1 mL 0.2% chlorhexidine in water. The teeth in both groups will be closed with a sterile dry cotton pellet and a minimum of 3 mm of temporary restorative material.

6. In the next appointment, the tooth was reopened, the intra-canal paste will be removed and a patency file (size 08 Flexofile; Dentsply-Maillefer) was pushed through the foramen.

Master apical file will be checked again and then master cones will be placed and radiographed. Obturation will be done using lateral compaction technique with AD seal resin sealer using spreader for placement of auxiliary cones.

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