The hardest bone in the human body is the mandible, which is more commonly known as the jawbone. This bone is also the largest and strongest bone in the human face. The jawbone sits in the lower portion of the face and holds the bottom teeth in place. It connects to the skull behind the ears.
The jawbone is a curved bone that joins with two temporal bones at the temporomandibular joints. The jawbone also contains the inferior alveolar nerve. This nerve is a branch of the trigeminal cranial nerve. It enters the mandibular foramen and runs through the mandible to provide the bottom teeth with sensation. At the mental foramen, the inferior alveolar nerve branches into two different nerve bundles that supply feeling and sensation to the lower lip. The entire jawbone forms while fetuses are in utero. During this time, cartilage forms first, and then the cartilage is ossified to form bone. Ossification takes place over several weeks. By birth, babies contain full mandibles that are broken into two distinct parts. The two parts are connected by a fibrous symphasis. This portion of the mandible fuses together through ossification during the first year of a child's life. This final ossification causes the mandible to become hard and strong.