FIGURE 3.10 Mental nerve and innervated area.

PATIENT POSITION

Supine on the examination table with the head of the bed slightly elevated.

LANDMARKS

With the patient supine on the examination table, the clinician stands lateral to the side of the face that is being injected.
In an anatomic study of skulls, mental foramina were on average, 25.8 mm lateral to the midline and about 13 mm superior to the inferior mandibular margin and along a line drawn in a vertical (sagittal) orientation from the center of the patient’s pupil.¹ A depression in the mandible at the site of the foramen is difficult to palpate. To confirm the location, firm pressure directly over the foramen elicits the sensation of intense, dull pain, not found in adjacent areas.
At that site, press firmly on the skin with the retracted tip of a ballpoint pen. This indention represents the entry point for the needle.

ANESTHESIA

Usually, topical vapocoolant spray is used to decrease the pain associated with injection. Alternatively, skin distraction methods may be employed.

EQUIPMENT

Headlamp or other light source (for intraoral approach)
3-mL syringe
30-gauge, 1/2-in. needle for transdermal and a 25-gauge 1½-in. needle for intraoral approach
1 mL of 1% lidocaine without epinephrine
One alcohol prep pad (for transdermal approach)
Sterile gauze pad

TECHNIQUE (TRANSDERMAL)

1. Prep the insertion site with alcohol pads.

2. Position the needle perpendicularly to the skin at the location over the mandible identified above. The tip of the needle is directed toward the mental foramen.

3. Provide skin distraction by pinching, stretching, and rubbing adjacent skin at the same time that the needle is being inserted into the skin.

4. Using the no-touch technique, quickly introduce the needle at the insertion site.

5. Advance the needle over the mental foramen.

6. Inject 0.5 to 1 mL of 1% lidocaine directly over the mental foramen.

7. Following injection, withdraw the needle.

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