Where is the mental foramen located?
The foramen is located beneath the mucosa on the lateral surface of the mandibular body (corpus mandibulae), approximately midway between the alveolar and inferior borders of the mandible. The canal opening faces posteriorly, superiorly, and laterally.
The shape of the foramen is oval or round, with dimensions varying from 1.5×2 mm to 3×7 mm. The distance from the inferior border of the mandible ranges from 3 to 21 mm. In some cases, two foramina may be present on each side.
Its topography relative to the tooth roots is variable:
- Below the second premolar — the most common location (54.5% on the right and 42.3% on the left).
- Between the first and second premolars — occurs in 22.5–30.3% of cases.
- Below the first premolar — observed in 11.1–15.9% of cases.
- Posterior to the second premolar or in the canine region — alternative variant localizations.
The foramen also lies on the same vertical facial line as the pupil (when the patient is gazing straight ahead), the oral commissure, and the supraorbital/infraorbital notches.
What passes through the mental foramen?
The foramen serves as the exit point from the mandibular canal (canalis mandibulae) for the corresponding neurovascular bundle (a., v. et n. mentales):
- Mental nerve (n. mentalis) — a large terminal branch of the inferior alveolar nerve. It provides sensory innervation to the skin and mucous membrane of the lower lip, as well as the skin of the chin.
- Mental artery (a. mentalis) — a branch of the inferior alveolar artery. It supplies the tissues of the chin and lower lip. On the face, it anastomoses with the inferior labial artery (a. labialis inferior) and submental artery (a. submentalis).
Clinical significance in dentistry and surgery
- Local anesthesia: The foramen serves as the target point for mental nerve block (mental anesthesia). Both extraoral and intraoral techniques are used. To achieve complete anesthesia of the premolars, canine, incisors, and alveolar process, the needle must be inserted directly into the canal to a depth of 3–5 mm, during which the clinician feels a characteristic 'give' or pop. If the needle is not inserted into the canal, only the soft tissues of the lip and chin are anesthetized.
- Surgical interventions: When draining subperiosteal abscesses in the premolar region, the incision should be arcuate with the apex pointing superiorly and closer to the gingival margin. The periosteum must be reflected with extreme caution to avoid damaging the exiting neurovascular bundle.
- Neurology: Congenital or acquired narrowing of the mental foramen can be a contributing factor to peripheral trigeminal neuralgia.