We compared the anesthetic efficacy of inferior alveolar nerve blocks (IANBs) with that of buccal infiltrations (BIs) in mandibular first molars. Using a crossover design, all subjects received a standard IANB or a BI of 1.7 mL of 4% articaine with 1:100,000 adrenaline (Septanest; Septodont, Saint-Maru-des-Fosses, France) on two appointments separated by at least 1 week. Pulpal anesthesia was determined by using an electric pulp tester. Electric pulp testing was repeated at 5, 8, 11, 15, 20, 25, and 30 minutes after the injections. Anesthesia was considered successful if the subject did not respond to the maximum output of the pulp tester at two or more consecutive time points. Fifty-four percent of the BI and 43% of the IANB were successful; the difference was not significant (p = 0.34). The onset of pulpal anesthesia was significantly faster with BI (p = 0.03). In conclusion, BI with 4% articaine for mandibular first molars can be a useful alternative for clinicians because compared with IANB it has a faster onset and a similar success rate.