Inferior Alveolar Nerve Block Using the Anterior Technique to Anesthetize Buccal Nerve and Improve Anesthesia Success Rates for Third Molar Extraction: A Randomized Controlled Trial and Magnetic Resonance Imaging Evaluation

Abstract

The lack of anesthesia to the buccal nerve and an insufficient volume of anesthetic have been reported to be responsible for failed inferior alveolar nerve blocks (IANBs) using the Halsted approach (conventional IANB). We aimed to determine the extent of anesthesia in the buccal nerve innervation area and evaluate the anesthetic efficacy of injecting a larger volume of anesthetic during IANB using the anterior approach (anterior technique) in the clinical setting and with magnetic resonance imaging (MRI) analysis. The prospective randomized controlled trial included patients scheduled for removal of a mandibular third molar. The primary predictor variables were the approach for IANB (anterior technique vs conventional IANB) and anesthetic dose (1.8 vs 2.7mL). The primary outcome variables were the extent of anesthesia and the anesthesia success rate, defined as completion without additional anesthesia. The secondary outcome variable was the anesthetic drug distribution related to the pterygomandibular space measured on T2-weighted MRI scans. Statistical independence of the anesthesia success rate among the primary predictor variables was tested with statistical significance set at P≤.05. A total of 108 patients and 10 volunteers were enrolled in the clinical and MRI studies, respectively. Anesthesia of the buccal nerve was evident in patients receiving the anterior technique with 2.7mL of anesthetic. The success rate of the anterior technique with 2.7mL of anesthetic (96%) was greater than that with 1.8mL of anesthetic (67%; P=.0113), and increasing the dose had no effect on the efficacy of conventional IANB (78% vs 81%; P=1.000). The MRI study showed that the anesthetic was distributed over the anterior surface of the temporalis tendon and in the pterygomandibular space after the anterior technique. Anesthesia of the buccal nerve using the anterior technique with 2.7mL of anesthetic solution might contribute to increasing the success rate of anesthesia for removal of mandibular third molars.