The base is the lowest, thickened part of the body of the mandible. Each of its surfaces features different landmarks described below. In craniometry, the midpoint on the lower border of the body is known as the gnathion.

Anatomical landmarks of external surface

The external surface of the mandibular base has the following landmarks:

Mental protuberance - a triangular-shaped eminence at the midline of the body that forms the chin;
Mental tubercle (2) - small bony prominence on each side of the mental protuberance;
Mental foramen (2) - a large opening located usually below the second mandibular premolar; it transmits the mental vessels and nerve; sometimes there are multiple foramina instead of one opening;
Oblique line (2) - a weak bony crest that extends into the body from the root of the ramus; it usually ends posterior to the mental foramen.

Note: The mental foramen is an important landmark, as it allows access to the mental nerve for local anesthesia. The mental nerve is a branch of the inferior alveolar nerve, which arises from the mandibular nerve (CN V3).

Anatomical landmarks of internal surface

The features found on the internal surface of the mandibular base are as follows:

Note: Sometimes, the mandible can have a bony, non-tender outgrowth on the inner surface of the body called the mandibular torus. It is usually found in the canine or premolar region above the attachment of the mylohyoid.

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Lower jaw (base of mandible)