Ninety patients with irreversible pulpitis diagnostic will participate in this clinical study. The participants will be divided into 2 groups of 45 patients, who will receive the inferior alveolar nerve block injections of 1.8 mL of 4% articaine (Articaine 100; DFL, Rio de Janeiro, RJ, Brazil) with 1:100,000 epinephrine or 3.6mL of the same solution. Two consecutive negative responses to the maximum pulp stimulus (80 µA) at the electric pulp test were the criterion to determine a pulpal anesthesia as successful. Ten minutes after the IAN block, subjective lip anesthesia will be evaluated by asking the patient whether his/her lip was numb. Thereafter and immediately before the pulpectomy, the electric pulp stimulations will be repeated to determine pulpal anesthesia. During the pulpectomy procedure, the patients were instructed to report any painful discomfort. To evaluate the intensity of pain during the pulpectomy, a verbal analogue scale will be used. The anesthesia will be defined as successful when the dentist accessed the pulp chamber without pain being reported by the patient. In these cases, the pulpectomy will be continued. If report pain will classified the IAN block as unsuccessful.

Ninety patients will Participate in this clinical study. The patients will be admitted to the Emergency Center of the School of Dentistry at the University of São Paulo with a clinical diagnosis of irreversible pulpitis, The study was approved by the Committee on the Ethics of Research on Human Beings of the School of Dentistry at the University of São Paulo (protocol 95/07), and each patient will be informed to sing consent to participate in the study. The 90 participants will be divided into 2 groups of 45 patients, who will receive the inferior alveolar nerve block injections of 1.8 mL (equivalent to 1 cartridge) of 4% articaine (Articaine 100; DFL, Rio de Janeiro, RJ, Brazil) with 1:100,000 epinephrine or 3.6mL (equivalent to 2 cartridges) of the same solution. Two consecutive negative responses to the maximum pulp stimulus (80 µA) at the electric stimulation were the criterion to determine a pulpal anesthesia as successful. Before the IAN block injections, the tooth with irreversible pulpitis, the adjacent tooth, and the contralateral canine will be tested for pulp vitality with an electric pulp test (Vitality Scanner 2006; SybronEndo, Orange, CA). The electric pulp stimulation of the contralateral canine, which will be not anesthetized, will be used as control to ensure that the equipment is working properly and that patients is responding adequately.

The average injection time for each cartridge was approximately 2 minutes. Ten minutes after the IAN block, subjective lip anesthesia will be evaluated by asking the patient whether his/her lip was numb. Thereafter and immediately before the pulpectomy, the electric pulp stimulations will be repeated to determine pulpal anesthesia. During the pulpectomy procedure, the patients were instructed to report any painful discomfort. To evaluate the intensity of pain during the pulpectomy, a verbal analogue scale will be used: 0, no pain; 1, mild, bearable pain; 2, moderate, unbearable pain; 3, severe, intense, and unbearable pain. The anesthesia will be defined as successful when the dentist accessed the pulp chamber without pain being reported by the patient (pain scores 0 or 1). In these cases, the pulpectomy will be continued. Pain scores of 2 or 3 will classified the IAN block as unsuccessful.

Inclusion Criteria:

• Patients 18-50 years, with mandibular molars with irreversible pulpitis, and have 1 molar adjacent to a molar presenting irreversible pulpites and a healthy contralateral canine with no deep carious lesions, extensive restoration, advanced periodontal disease, a history of trauma, or sensitivity.

Exclusion Criteria:

• Patients who took medication potentially interacting with the anesthetic used in the study