A jaw is either one of the two opposable bony structures forming the entrance to the mouth, and which usually contain teeth. There is a movable lower jaw called mandible, and an upper jaw fixed to the skull called maxilla.
Both mandible and maxilla move in opposition to each other, which gives them the functions of biting, chewing and handling food in the mouth.
The mandible is also called lower jaw, or jawbone, and it’s the largest and strongest bone in the human face. The mandible has teeth that develop on it, and it’s the only movable bone of the skull. It is formed by two mandibular bones that are fused in the middle at the mandibular symphysis (median line of junction marked by a faint ridge where the two lateral halves of the mandible usually fuse).
Mandibular fractures account of one fifth of facial injuries, and they are often accompanied by an identical fracture on the opposite side of the bone (twin fracture). Trauma may also dislocate a mandible, more often to the front, but also downwards, and rarely to the back.
As a person grows older, the bone in the mandible can become greatly reduced in volume where there is a loss of teeth. This is due to the resorption of the alveolar processes following tooth loss.
Also called upper jaw, the maxilla has teeth that develop on it as well, but unlike the mandible that is mobile, the maxilla is fixed to the skull. The maxilla is formed by two maxillary bones that are fused in the middle at the intermaxillary suture (median line of junction that extends from the front to the back of the maxilla, and that can be felt on the hard palate).
Maxillary fractures occur less often than mandibular ones, but may follow facial trauma such as falls, violence, or automobile accidents.
In old age, if a person has lost teeth, the bone can also become greatly reduced because of resorption of the alveolar bone.
TMJ, or temporomandibular joints, are the two joints that connect the mandible to the temporal bone of the skull. They are among of the most frequently used joints in the entire body, moving whenever a person eats, drinks, or talks.
Both joints function together and are not independent of each other, because the mandible is one body of bone.
Jaw diseases and pathologies
Temporomandibular disorders (TMD) are problems related to the muscles and nerves of the face that control the movement of the mandible. TMDs are expressed by pain or limitation of opening of the mouth. The exact causes TMDs are unclear, but we believe that symptoms arise from problems with the muscles, and parts of the TMJ itself (temporomandibular joint). It is also suspected that TMDs can be related to bruxism (teeth grinding), arthritis, and stress which causes clenching. In some cases, a nightguard may help to reduce the symptoms of TMDs.
Impacted wisdom teeth is a condition that happens more often in person’s of today’s society. It is the fact that 3rdmolars remain inside the jaw because they have no space to come out and do normal eruption. When this happens, it is often advised to have them extracted in order not to cause future problems.
Oral cancers are tumours that affect numerous parts of the mouth, including both the maxilla and the mandible. Oral cancers affecting the jaws can sometimes be detected on routine panoramic x-rays, or other dental x-rays. A biopsy of the suspected lesion should follow to make proper diagnosis.
- Brian S. Shumway, DDS, MS; Timothy S. Foster, DMD. (Pathology of the Jaw: The Importance of Radiographs). J Can Dent Assoc 2011;77:b132.
- WebMD, (Temporomandibular Joint Disorders (TMD, TMJ)).
- National Institute of Dental and Craniofacial Research, (TMJ (Temporomandibular Joint & Muscle Disorders)).
- American Family Physician, (Diagnosis and Treatment of Temporomandibular Disorders).
- Ashish Vyas, Utpal Mazumdar, Firoz Khan, Madhura Mehra, Laveena Parihar, and Chandni Purohit. (A study of mandibular fractures over a 5-year period of time: A retrospective study). Contemp Clin Dent. 2014 Oct-Dec; 5(4): 452–455.
- Hai-Won Jung, Baek-Soo Lee, Yong-Dae Kwon, Byung-Jun Choi, Jung-Woo Lee, Hyun-Woo Lee, Chang-Sig Moon, and Joo-Young Ohe. (Retrospective clinical study of mandible fractures). J Korean Assoc Oral Maxillofac Surg. 2014 Feb; 40(1): 21–26..
The information above should be used as a reference only. Any medical decision should not be taken before consulting a health care professional.