|Mandible. Lateral surface. Side view|
|Mandible. Medial surface. Side view|
|Gray's||subject #44 172|
|Precursor||1st branchial arch|
The mandible  (from Latin mandibula, "jawbone") or inferior maxillary bone forms the lower jaw and holds the lower teeth in place. In the midline on the anterior surface of the mandible is a faint ridge, an indication of the mandibular symphysis, where the bone is formed by the fusion of right and left processes during mandibular development. Like other symphysis in the body, this is a midline articulation where the bones are joined by fibrocartilage, but this articulation fuses together in early childhood.
The mandible consists of:
- a curved, horizontal portion, the body or base. (See body of mandible).
- two perpendicular parts, the rami, or ramus for each one, unite with the ends of the body nearly at right angles. (See ramus mandibulae). The angle formed at this junction is called gonial angle.
- Alveolar process, the tooth bearing area of the mandible (upper part of the body of the mandible)
- Condyle, superior (upper) and posterior projection from the ramus, which makes the temporomandibular joint with the temporal bone
- Coronoid process, superior and anterior projection from the ramus. This provides attachment to the temporalis muscle
- Mandibular foramen, paired, in the inner (medial) aspect of the mandible, superior to the mandibular angle in the middle of the ramus.
- Mental foramen, paired, lateral to the mental protuberance on the body of mandible, usually inferior to the apices of the mandibular first and second premolars. As mandibular growth proceeds in young children, the mental foramen alters in direction of its opening from anterior to posterosuperior. The mental foramen allows the entrance of the mental nerve and blood vessels into the mandibular canal.
Inferior alveolar nerve, branch of the mandibular division of Trigeminal (V) nerve, enters the mandibular foramen and runs forward in the mandibular canal, supplying sensation to the teeth. At the mental foramen the nerve divides into two terminal branches: incisive and mental nerves. The incisive nerve runs forward in the mandible and supplies the anterior teeth. The mental nerve exits the mental foramen and supplies sensation to the lower lip.
Rarely, a bifid inferior alveolar nerve may be present, in which case a second mandibular foramen, more inferiorly placed, exists and can be detected by noting a doubled mandibular canal on a radiograph.
Males generally have squarer, stronger, and larger mandibles than females. The mental protuberance is more pronounced in males but can be visualized and palpated in females. The symphysis can be not fully fused which happens more in male, leaving an indentation.
One fifth of facial injuries involve mandibular fracture. Mandibular fractures are often accompanied by a 'twin fracture' on the contralateral (opposite) side. There is no universally accepted treatment protocol, as there is no consensus on the choice of techniques in a particular anatomical shape of mandibular fracture clinic. A common treatment involves attachment of metal plates to the fracture to assist in healing.
- Motor vehicle accident (MVA) – 40%
- Assault – 40%
- Fall – 10%
- Sport – 5%
- Other – 5%
Location of mandibular fractures
- Condyle – 30%
- Angle – 25%
- Body – 25%
- Symphesis – 15%
- Ramus – 3%
- Coronoid process – 2%
The mandible may be dislocated anteriorly (to the front) and inferiorly (downwards) but very rarely posteriorly (backwards).
The mandibular alveolar process can become resorbed when completely edentulous in the mandibular arch (occasionally noted also in partially edentulous cases). This resorption can occur to such an extent that the mental foramen is virtually on the superior border of the mandible, instead of opening on the anterior surface, changing its relative position. However, the more inferior body of the mandible is not affected and remains thick and rounded. With age and tooth loss, the alveolar process is absorbed so that the mandibular canal becomes nearer the superior border. Sometimes with excessive alveolar process absorption, the mandibular canal disappears entirely and leaves the inferior alveolar nerve without its bony protection, although it is still covered by soft tissue.
|Wikimedia Commons has media related to Human anatomy, mandible.|
This article uses anatomical terminology, for an overview see anatomical terminology.
- Bone terminology
- Changes produced in the mandible by age
- Oral and maxillofacial surgery
- Ossification of the mandible
- Simian shelf
- Terms for anatomical location
- hednk-023 — Embryo Images at University of North Carolina
- Mandible on www.merriam-webster.com
- Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 59
- Levin L, Zadik Y, Peleg K, Bigman G, Givon A, Lin S (August 2008). "Incidence and severity of maxillofacial injuries during the Second Lebanon War among Israeli soldiers and civilians". J Oral Maxillofac Surg 66 (8): 1630–3. doi:10.1016/j.joms.2007.11.028. PMID 18634951. Retrieved 2008-07-16.
- Tiberiu Niță, Vasilios Panagopoulos, Laurențiu Munteanu, Alexandru Roman (Mar 2012). "Customised osteosynthesis with miniplates in anatomo-clinical forms of mandible fractures". Rev. chir. oro-maxilo-fac. implantol. (in (Romanian)) 3 (1): 5–15. ISSN 2069-3850. 59. Retrieved 2012-08-19.(webpage has a translation button)
- Marius Pricop, Horațiu Urechescu, Adrian Sîrbu (Mar 2012). "Fracture of the mandibular coronoid process — case report and review of the literature". Rev. chir. oro-maxilo-fac. implantol. (in (Romanian)) 3 (1): 1–4. ISSN 2069-3850. 58. Retrieved 2012-08-19.(webpage has a translation button)