• The aim of this study is to compare the degree of postoperative pain and the antimicrobial effect in terms of bacterial count reduction after using co-amoxiclav-clindamycin solution versus MTAD and sodium hypochlorite irrigating solutions in patients with necrotic pulp.

• After confirming the diagnosis and making sure that the patient conforms to all eligibility criteria, the principal investigator will enroll the patient in the study.

• The operator will complete treatment of all cases in two visits as follows:

  1. Anesthesia will be achieved using inferior alveolar nerve block for mandibular premolar teeth and infiltration technique for maxillary anterior teeth with local anesthesic solution of 1.8 mL of 2% Mepivacaine HCl with 1:100,000 epinephrine.

  2. Caries and/or coronal restorations will be completely removed with sterile bur and rubber dam will then be applied.

  3. The operative field, including the tooth, the clamp and rubber dam sheet will be cleaned with 30% hydrogen peroxide for 30 seconds, followed by a sterile cotton swab with 5.25% NaOCl for the same period of time and then inactivated with 5% sodium thiosulphate.

  4. Access cavity will be prepared using a sterile round carbide bur size 3 and a sterile Endo-Z bur.

  5. The operative field and the pulp chamber will be cleaned and disinfected once again in the same way mentioned above.

  6. Patency of the root canals will be achieved using #10 or #15 size stainless steel hand K-files. Working length (WL) will be determined using an electronic apex locator then confirmed radiographically to be 1 mm shorter than radiographic apex.

  7. Debridement and mechanical preparation will be performed with the initial file along with 2 mL of 0.9% sterile saline solution and then a pre-instrumentation sample will be collected from the root canal.

  8. The pre-instrumentation sample (S1) will be collected as follows: a sterile paper point will be placed inside the root canal to soak up the fluid in the canal to a level approximately 1 mm short of the tooth apex. The paper point will be left in the canal for 60 seconds. This will be repeated using three sterile paper points. Paper points will then be transferred aseptically to tubes containing 20 mL of sterile thioglycolate broth.

     Microbiological analysis To test for the presence of cultivable bacteria, cultures will be inoculated in thioglycolate broth. For the identification of main anaerobic taxa, the root canal samples will be plated on 5% sheep blood agar, neomycin blood agar and phenyl ethyl alcohol agar with metronidazole (5μg, Oxoid, Basingstoke, UK) disc. Cultures will be incubated at 37°C for 72 hours in an anaerobic chamber . In addition, specimens will also be cultured aerobically on 5% sheep blood agar and MacConkey's agar.

  9. Mechanical preparation will be completed in a crown down technique with Protaper Next rotary files set on an endodontic motor adjusted at a speed of 300 rpm and torque of 2 Ncm. In-and-out motions will be applied with stroke lengths not exceeding 3 mm in the cervical, middle, and apical thirds until attaining the established WL. All root canals will be enlarged to size X4 (40.06). The canal will be irrigated and recapitulated after the use of each instrument according to the allocated group as follows:

     Group 1: Alternate irrigation with 1 mL antibiotic-containing solution followed by 4 mL 2.5% sodium hypochlorite solution between each size instrument and the consequent one. The antibiotic-containing solution will be prepared by mixing equal quantities of 1.2 gm Co-amoxiclav solution and 600 mg Clindamycin solution at a ratio of 1:1 by volume.

     Group 2: Irrigation with 5 mL MTAD irrigating solution for 5 minutes between each size instrument and the consequent one.

     Group 3 (control): Irrigation with 5 mL 2.5% sodium hypochlorite irrigating solution between each size instrument and the consequent one.

  10. The root canal will be thoroughly irrigated with the allocated irrigant using a plastic disposable syringe with a gauge 30 side-vented needle reaching 1 mm short of the WL. The canal will then be dried using sterile paper points.

  11. Canals irrigated with NaOCl (groups 1 and 3) will be flushed with 5 mL of 5% sodium thiosulfate to inactivate the NaOCl followed by 5 mL 0.9% sterile saline solution. Canals irrigated with MTAD (group 2) will be flushed with 5 mL 0.9% sterile saline solution.

  12. A post-instrumentation sample (S2) will be taken as previously described and then the cavity will be sealed with a sterile cotton pellet and a temporary filling material .

  13. The patient will be instructed to record their pain level on NRS at 24 and 48 hours postoperatively and will be recalled after 72 hours. The patient will be prescribed Ibuprofen (400 mg) to be taken in case of intolerable pain.

  14. In the recall appointment, the root canal will be accessed under sterile conditions and will be flushed with 1mL sterile saline solution before a third sample (S3) is taken as previously described.

  15. Master cone fit radiograph will be taken and then the root canal will be dried using sterile paper points and filled with gutta percha points and resin-based sealer using cold lateral condensation technique.

  16. Access cavity will be sealed with a temporary filling material and the final restoration will be placed within one week.

  17. The patient will be asked to report any swelling, in such case, he/she will be appointed for clinical examination to assess the severity by a blinded assessor and to determine if systemic antibiotics/drainage will be needed.

Inclusion Criteria:

• Maxillary/mandibular single-rooted permanent teeth:

  • Diagnosed clinically with pulp necrosis.
  • Absence of spontaneous pain.
  • Normal/slight widening in the periodontal membrane space (PMS).

• Patients' acceptance to participate in the trial.

• Patients who can understand numerical rating scale (NRS) and can sign the informed consent.

Exclusion Criteria:

• Medically compromised patients: Pain levels and healing following treatment would be compromised as these patients show higher incidence of pain and lower healing rate.
• Patients with known allergy to penicillin or penicillin derivatives.
• Pregnant females: Avoid radiation exposure, anesthesia, and medication.
• If analgesics or antibiotics have been administrated by the patient during the past 24 hours preoperatively: Might alter their pain perception.
• Patients reporting bruxism or clenching: Avoid further pressure on an already inflamed tooth inducing subsequent irritation and inflammation.
• Teeth that show association with acute periapical abscess and swelling: Need special treatment steps which could involve additional visits with incision and drainage. Also, it could influence initiation and progression of postoperative pain.
• Greater than grade I mobility or pocket depth greater than 5mm. Need special surgical and/or periodontal therapy.
• Non-restorable teeth.
• Immature teeth.
• Radiographic evidence of periapical radiolucency, external or internal root resorption, vertical root fracture, perforation or calcification.