A mental nerve block will anesthetize the lower lip and skin of the chin, as well as the gums and buccal mucosa.
The mental nerve is a branch off of the inferior alveolar nerve and exits the mandible through the mental foramen. You can see there’s a lot of overlap between the mental nerve and the inferior alveolar nerve, and that’s because it’s the same nerve! The inferior alveolar is just more proximal, so it also includes the teeth and often the tongue due to diffusion into the lingual nerve.
The mental foramen is inferior to the second premolar, which can be easily palpated. To find the second premolar count back: central incisor, lateral incisor, canine, first premolar, second premolar. It’s the 5th tooth back. Then slide down to the foramen. You can inject here through the skin, but the intraoral approach is preferred.
Before an intraoral injection, I recommend applying topical lidocaine to the site, which can be done with viscous lidocaine on a 2x2 gauze or with a commercially available lidocaine product, leaving it in place for a couple of minutes.
Using a 25-27 gauge inch needle, aim towards the foramen, angling at about 45 degrees. We are not trying to shove the needle into the foramen, as that can cause nerve injury. The perfect block would infiltrate just around the foramen. Inject about 2 mL of local anesthetic.
Peer Reviewed by Britt Guest, DO, Mel Herbert, MD, Stuart Swadron, MD, and Jessie Werner, MD.