Objective: The purpose of this study was to clinically evaluate an anesthetic technique in which a second cartridge was reloaded in a traditional dental syringe and reinjected at the same site in regard to success rate of the attempted inferior alveolar nerve block. During the same appointment, a computer-controlled delivery system was used on the opposite side of the same patient to administer 2 cartridges as well. Successful anesthesia and time efficiency of the traditional syringe and computer-controlled technique were then evaluated and compared. Method and Materials: Thirty-five subjects between the ages of 18 and 58 years were randomly assigned to both the traditional syringe delivery system using a standardized 2-cartridge reloading and reinjection technique and a computer-controlled system using a technique whereby the second cartridge was reloaded without having to remove the needle from the injection site. Subjects served as their own controls. Successful anesthesia was achieved when all soft tissues innervated by the inferior alveolar and lingual nerves were nonresponsive to painful stimulation with an explorer as evaluated at 3- and 10-minute intervals following final anesthetic administration. The time necessary to reload the second cartridge for each side was measured, as was the time necessary to deliver the second full 1.8-mL cartridge. Results: Two-cartridge delivery with the traditional syringe resulted in a 94.3% success rate at 3 minutes and a 100% success rate at 10 minutes; 2-cartridge delivery with the computer-controlled delivery system resulted in an 80% success rate at 3 minutes and a 91.4% success rate at 10 minutes following final injection. Reloading time for the second cartridge was 11.37 seconds less with the computer-controlled delivery system, but no statistical difference was found between the 2 systems regarding time to deliver the second cartridge. Conclusions: The results for the 2-cartridge technique with both systems compare favorably with and surpass the accepted 85% success rate reported in the dental literature with only 1 cartridge. The computer-controlled delivery system did not require needle removal and was more time efficient at reloading than the traditional syringe system. Schlagwörter: computer-controlled delivery system, dental anesthesia, inferior alveolar nerve block, local anesthesia, success rate, two-cartridge injection