Objective: To compare the success of an inferior alveolar nerve block (IANB) after injecting a combination of mepivacaine + tramadol, mepivacaine alone, or lignocaine in patients with symptomatic irreversible pulpitis (SIP) in mandibular permanent molars. Materials and methods: Three study groups, each consisting of 30 patients exhibiting SIP on the first or second mandibular molars were assessed for preoperative pain according to a modified Heft-Parker visual analogue scale (VAS). Patients were anaesthetised using the IANB technique by administering identical cartridges containing either: 1.3 ml of 3% mepivacaine plain + 0.5 ml of 50 mg/ml tramadol; 1.8 ml of 3% mepivacaine; or 1.8 ml of 2% lignocaine with 1:100,000 adrenaline. After 15 minutes, lip numbness was confirmed and the efficacy of anaesthesia was evaluated by a progressive four-test examination; namely, pulp sensibility cold test, presence of pain when manipulating dental hard tissues (access opening), and accessing the pulp within chamber and root canals. The success of IANB was defined as the absence of pain during any of these evaluations. The Kruskal-Wallis test to compare mean pain scores among the groups, and the Wilcoxon signed-ranks test for pairwise VAS (pre- and post-anaesthesia) comparison were applied. Results: The success rates of anaesthesia were 70%, 53% and 57% for mepivacaine-tramadol, mepivacaine alone and lignocaine groups, respectively, which was not statistically significant (P > 0.05). Conclusion: The three anaesthetics tested achieved similar success for IANB in SIP patients, with no statistically significant difference. Keywords: inferior alveolar nerve block, lignocaine, mepivacaine-tramadol, symptomatic irreversible pulpitis, visual analogue pain scale