Background. A single palatal–anterior superior alveolar, or P-ASA, injection has been reported to provide pulpal anesthesia of the four maxillary incisors and usually the canines. The authors conducted a prospective, randomized, double-blind study to compare the anesthetic efficacy of 2 percent lidocaine with 1:100,000 epinephrine and 3 percent mepivacaine using a computer-assisted injection system to administer the P-ASA injection.
Materials and Methods. In a double-blind manner, the authors used a crossover design to administer randomly P-ASA injections of 1.4 milliliters of the lidocaine solution and 1.4 mL of the mepivacaine solution using the computer-assisted injection system at two appointments to 40 subjects. They used a pulp tester to test for anesthesia of the central incisors, lateral incisors and canines in four-minute cycles for 72 minutes. Anesthesia was considered successful when two consecutive maximum readings (80 readings) with the pulp tester were obtained.
Results. For the lidocaine solution, successful pulpal anesthesia ranged from 32 to 58 percent for the six anterior teeth. For the mepivacaine solution, successful pulpal anesthesia ranged from 22 to 38 percent. Except for the left canine, the lidocaine solution was significantly more likely to result in pulpal anesthesia than the use of the mepivacaine solution. The duration of pulpal anesthesia, for both solutions, declined steadily over 72 minutes.
Conclusions and Clinical Implications. Using the computer-assisted injection system for the P-ASA injection, we concluded that the rather modest-to-low success rates of the lidocaine and mepivacaine solutions would not ensure predictable pulpal anesthesia of the four maxillary incisors and the canines.
