Mental nerve and mental foramen: anatomy of the chin
- Artery
- Nerve
- Highlighted area
Quick facts
- Origin
- Terminal branch of the inferior alveolar nerve, which comes from the mandibular nerve (V3) of the trigeminal.
- Foramen
- On the outer surface of the mandible, usually below the lower premolars, with variation.
- Sensory supply
- Skin of the chin, skin and mucosa of the lower lip and anterior buccal gum.
- Accompanying vessels
- Mental artery and vein, which exit through the same foramen.
- Relevance in facial harmonization
- Neighbor of chin filler and the pre-jowl sulcus; injury causes lower lip paresthesia.
The mental nerve is the terminal branch of the inferior alveolar nerve, which in turn comes from the mandibular nerve (V3), the third division of the trigeminal nerve. It exits the mandible through the mental foramen, below the lower premolars, and carries sensation from the lower lip and the skin of the chin. It is sensory: it does not move muscles. Injury to it causes numbness or tingling in the lower lip, the main complaint tied to this structure.
Where is the mental foramen?
| Reference | Usual description |
|---|---|
| Horizontal position | Below the second lower premolar or between the first and second |
| Height in an adult with teeth | About halfway between the alveolar crest and the lower border of the mandible |
| With bone resorption | Tends to sit higher, near the crest, in people without teeth |
| Vertical line | Roughly in line with the pupil and the infraorbital foramen |
| Variation | Accessory foramina and differences between sides are described |
The nerve exits the foramen heading up and back and divides under the depressor anguli oris muscle, sending branches to the skin of the chin and the lower lip up to the midline.
What does the mental nerve supply?
- Chin skin: the chin region in front of and beside the midline.
- Lower lip: skin, vermilion and mucosa.
- Anterior buccal gum: from the premolar region to the midline.
The lower front teeth receive sensation through the incisive branch, which continues inside the bone. That is why mental and incisive nerve anesthesia is used in dentistry, and the mental block is cited for anesthetizing the lower lip. The overview, without a protocol, is in local anesthesia in facial harmonization.
Why does it matter in facial harmonization?
- Chin and contour filler: the foramen lies lateral to the central chin area and close to the pre-jowl sulcus. Volume that compresses the region, or direct trauma, can cause lower lip paresthesia.
- Vessels that exit alongside: the mental artery, a branch of the inferior alveolar artery, communicates with the inferior labial artery and the submental artery. Bleeding and ecchymosis are possible in the area.
- Mentalis toxin: toxin in the chin acts on the mentalis muscle, which is motor and supplied by the facial nerve. Lip numbness is not an expected toxin effect and deserves investigation.
How does it show up in the assessment?
- Prior lip sensation: third molar extractions, implants and jaw surgery may have left some change, which must be recorded beforehand.
- Dental status: in people without posterior teeth, the foramen tends to sit higher.
- Imaging: existing dental radiographs usually show the foramen and help in understanding the patient's anatomy.
The area is covered in chin, and the procedure in chin filler.
Also called: mentonian nerve, mentonian foramen, nervus mentalis.
Frequently asked questions
Where is the mental foramen?
On the outer surface of the mandible, usually below the second lower premolar or between the first and second, roughly halfway up the bone in an adult with teeth. With tooth loss and bone resorption, it tends to sit closer to the crest.
Does lower lip paresthesia after filler go away?
When the cause is compression or irritation of the mental nerve, the condition usually improves with time, over weeks to months, but it varies. It needs to be assessed by the professional, recorded and followed up, and management depends on the cause.