Patient-friendly definition from the DentistsDirectory.org dental glossary.
The mandible is the lower jaw — a U-shaped bone that holds the lower teeth and is the only bone in the skull capable of independent movement. It is connected to the rest of the skull on each side through the temporomandibular joint (TMJ), located just in front of each ear. The mandible moves in three dimensions: up and down for biting, forward and back, and sideways for chewing — all controlled by the powerful muscles of mastication including the masseter and temporalis.
The mandible consists of the horizontal body (which holds the lower teeth), two vertical rami that rise on each side to connect to the skull at the TMJ, and the chin prominence at the front (the symphysis menti). The alveolar process — the portion that contains the tooth sockets — is the most susceptible to bone loss from gum disease. The mandibular canal runs through the body of the jaw on each side, carrying the inferior alveolar nerve and blood vessels; dentists must be aware of its position when extracting lower molars or placing implants to avoid damaging this nerve.
The mandible is the most commonly fractured bone in the face, typically from falls, sports injuries, or vehicle accidents — it protrudes and absorbs impacts that would otherwise reach more critical structures. Fractures require specialist management, often with surgical fixation. Significant bone loss from gum disease, long-term tooth absence, or ill-fitting dentures can substantially reduce mandibular bone volume, which complicates implant placement and affects facial appearance by reducing the lower third of the face.