Using a crossover design, 60 adult subjects will receive three injections consisting of a primary mandibular first molar infiltration of 1.8 mL of 4% articaine with 1:100,000 epinephrine, 1.8 mL of 4% prilocaine with 1:200,000 epinephrine, and 1.8 mL of 4% lidocaine with 1:100,000 epinephrine in three separate appointments spaced at least one week apart. With the crossover design, 180 infiltrations will be given for the first molar and each subject will serve as his or her own control. Ninety infiltrations will be administered on the mandibular left side and ninety administered on the mandibular right side. The order of the three injections will be assigned randomly and the dentist and subject will be blinded about which anesthetic the subject is given. The anesthetics used in this study are not experimental. An electric pulp tester will be used to test the lower back teeth (molars and premolars) for anesthesia in 3-minute time intervals for a total of 60 minutes. The pain of injection and postoperative pain will be recorded in a survey. The data will be statistically analyzed.