The aim of this prospective randomized clinical trial was compare between 2% Mepivacaine and 4% Articaine for inferior alveolar nerve blocks in patients with symptomatic irreversible pulpitis in mandibular molars as regards to their anesthetic efficiency; during access cavity preparation and instrumentation.

Sixty-six patients diagnosed clinically and radiographically with symptomatic irreversible pulpitis in mandibular posterior teeth will received single-visit root canal treatment using ProTaper Universal rotary system for canal preparation, then they will be randomly divided into two groups (n=33) according to the anesthetic solution used, either Group M (3.6 ml Mepivacaine hydrochloride 2% with 1:100000 epinephrine) or Group A (3.4 ml Articaine hydrochloride 4% with 1:100000 epinephrine). The pain will be assessed using numerical rating scale (NRS) during access cavity preparation and instrumentation, then the need for supplemental anesthesia will be also recorded.

Inclusion Criteria:

1. Patients in good health (American Society of Anesthesiologists Class II or higher)
2. Patients having symptomatic irreversible pulpitis in one of their mandibular molars.
3. Age range is between 20 and 50 years.
4. Patients who can understand Visual Analogue Scales VAS.
5. Patients able to sign informed consent

Exclusion Criteria:

1. Patients allergic to articaine and/or mepivacaine and/or sulfur
2. Patients having active sites of pathosis in the area of injection.
3. Patients having active pain in more than one molar.
4. Patients who had taken analgesics in the 12 hours preceding the injection.