Reversing the Effects of 2% Lidocaine: A Randomized Controlled Trial

The research will be conducted at the Dalhousie University Dental Clinic. As part of their anaesthesia clinical course, students enrolled in the second year of the dentistry and dental hygiene programs practice different anesthesia techniques on each other during a planned hands-on training activity. The research study will take place during the same day. Participants who meet the eligibility criteria and consent to participate will be randomly assigned to one of two groups. Following anesthesia obtained as a part of their hands-on training session, subjects allocated to Group 1 will receive 1ml of phentolamine mesylate following anesthesia, while subjects allocated to Group 2 will receive 1ml of sterile physiological water.

Phase 1, Both Groups:

1. Subjects will be trained to use the Assessment of Anesthesia questionnaire
2. Following training, subjects will perform baseline assessments of their lip and tongue numbness (should be normal).
3. Prior to anaesthesia is given, vital signs will be recorded. Blood pressure, respiratory rate and pulse will all be recorded.
4. Topical anesthetic, 20% benzocaine, will be applied to the injection site for 3 minutes. Subjects will be given a standard inferior alveolar nerve block injection, with aspiration before injection, using 1ml of 2% lidocaine with 1:100,000 epinephrine from the student they are teamed with. This step is not part of the study; it is done as part of their clinical anesthesia course.
5. Soft tissue anaesthesia will be self-assessed, by using finger tapping and palpation, to ensure profound anesthesia. The second phase (OraVerse or water) will not take place before profound anesthesia has been achieved. The anesthetic outcome will be considered a failure if the participant does not report anesthesia of the lower lip within 10 minutes.
6. If profound anesthesia is achieved within 10 minutes, subjects will proceed to phase 2. If profound anesthesia is not achieved within 10 minutes subjects will be withdrawn from the study. Subjects who are withdrawn from the study will continue with their standard training protocol which is to receive a re-injection of anesthetic. A withdrawal form will be used by Dr. Flood to record the occurrence of anesthesia failures. This form will also record reasons for withdrawals, should any occur for different reasons.

Phase 2 Group 1: Phentolamine Mesylate After anesthesia is confirmed, subjects in Group 1 will receive an injection of 1ml of a solution containing 0.24mg of phentolamine mesylate in the same site previously injected with anaesthetic solution. Dr. Brittany Flood will give the injection to ensure consistency.

Group 2: Water After anesthesia is confirmed, subjects in Group 2 will receive an injection of 1ml of sterile physiological water in the same site previously injected with anesthetic solution. Dr. Brittany Flood will give the injection to ensure consistency.