The Anesthetic Challenge Test involves isolating or mapping out the painful area, asking the patient to rate their ongoing spontaneous pain, and then applying a topical anesthetic (such as benzocaine gel).
If the pain does not resolve with topical anesthetic, this lowers the chances of the sustained application of a topical anesthetic will be therapeutic and reversing the neuropathic changes. In these cases, the next step is to perform a local infiltration of anesthetic in the area to see if the pain can be stopped.
When a single anesthetic infiltration or nerve block fails, the neural changes are considered more substantial, and it is more likely that central sensitization has developed (i.e., 2nd and 3rd order neuronal changes). This result suggests that the magnitude of peripheral and central change is such that the patients will require systemic (usually anticonvulsant) medications in addition to topical anesthetics to manage chronic pain.
*Note: Atypical Odontalgia patients might not experience complete pain relief from the administration of local anesthetics, indicating that the spontaneous pain is not only dependent on peripheral afferent inputs but also on sensitization of higher-order neurons.
Bavarian R, Khawaja SN, Treister NS. Oral Appliances in the Management of Neuropathic Orofacial Pain: A Retrospective Case Series. Oral Dis. 2021 Mar 1. doi: 10.1111/odi.13824. Epub ahead of print. PMID: 33650141.
List T, Leijon G, Helkimo M, Öster A, Svensson P. Effect of local anesthesia on atypical odontalgia--a randomized controlled trial. Pain. 2006 Jun;122(3):306-314. doi: 10.1016/j.pain.2006.02.005. Epub 2006 Mar 29. PMID: 16564621.