the study is conducted to assess the effect of adding magnesium sulphate to mepivacaine HCl compared to mepivacaine HCl alone on the success of inferior alveolar nerve block in patients with symptomatic irreversible pulpitis in mandibular molars

Inclusion Criteria:

1. Age between 18-55 years old.

2. Systemically healthy patient (ASA I or II).

3. Mandibular molar teeth with:

   • Preoperative sharp pain.
   • No widening in the periodontal ligament (PDL).
   • Vital response of pulp tissue to cold pulp tester (ethyl chloride spray)1.
   • Fully formed roots.

4. Positive patient's acceptance for participation in the study.

Exclusion Criteria:

1. Patients who had used any type of analgesic medication during the preceding 12 hours before the treatment.
2. Pregnant or nursing females.
3. Patients having significant systemic disorder (ASA III or IV).
4. Drug abusers and subjects who were on antidepressant medication.
5. Re-treatment cases.
6. Patients with a contraindication for the use of magnesium sulphate or those known to be allergic to any of the study medications.