A pilot study comparing the accuracy of two approaches to the inferior alveolar nerve block in canine cadavers

Aims The inferior alveolar nerve block provides sensory blockade of the body of the mandible and its associated structures. Two approaches, the intraoral and extraoral techniques, can be used. We hypothesized that the intraoral approach would result in a more accurate placement of solution at the inferior alveolar nerve. Methods Five canine cadavers (10-15 kg) were used. A random number generator was used to randomly assign the right-sided approach (intraoral or extraoral) for each head; the opposite approach was performed on the left. Blocks were performed using 22 g, 2.5 cm needles, 0.1 mL of 2% lidocaine and 0.3 mL of iodinated contrast medium. After blocks, computed tomography (CT) was performed on each head. Heads were positioned in the dorsoventral position for the CT scan Computed tomographic images were evaluated for the percent of the mandibular foramen in contact with contrast, distance of contrast from the foramen, length of spread of contrast along the inferior alveolar nerve fascial plane, and degree of contrast between the mandibular lingual tissue planes. A Chisquare test was used to evaluate contrast between the mandibular lingual tissue. All other measurements were compared using the Wilcoxon-Mann-Whitney Test. Results Median contact with the inferior alveolar nerve (p=0.025) and percentage of mandibular foramen in contact with contrast pool(p=0.009) was significantly greater for the intraoral approach. Clinical Relevance The intraoral approach to the inferior alveolar nerve block demonstrates greater accuracy of local block placement when compared with the extraoral approach. Thus suggesting the intraoral approach decreases risks associated with inaccurate placement and may improve clinical efficacy. Conclusions The intraoral technique showed superior precision with low volume injectate in cadaver dogs with normal anatomy, when compared with the extraoral approach.