Mandible (the lower jaw)

The mandible also known as the jawbone is the lower jaw of the human skeleton and is the largest and strongest bone of the face. The mandible serves as a fixing area for the lower teeth and consists of a curved horizontal portion called the body and two perpendicular portions called the rami. Each of these important parts of the lower jaw are explained below:

The Body (corpus mandibul�)

The body is curved like a horseshoe and has two surfaces and two borders. The two surfaces are the external surface and in the internal surface. The borders of the lower jaw are called the superior or alveolar border and the inferior border.

The Ramus (ramus mandibul�; perpendicular portion).

The Ramus is quadrilateral in shape and has two surfaces and four borders. The two surfaces are called the lateral surface and the medial surface. The four borders are called the lower border the anterior border the posterior border and the upper border.

Over time the mandible changes to accommodate the eruption of new teeth. The main changes in the mandible occur at birth after birth (0yrs-6yrs) during adult age (17yrs-35yrs) and during old age (50yrs+).

There are many problems associated with the mandible and abnormal growth of the mandible can lead to the following problems:


This is where the mandible has not grown as much as it should resulting in a small mandible and chin. This can be corrected with advancement of the mandible and advancement of the chin surgically. The correction is done intraorally without any incisions on the face and it is preceded by orthodontic treatment to align the teeth prior to proper surgical treatment.


This is when the lower jaw is too prominent leading to a prognathic mandible and occurs with inherited overgrowth of the lower jaw as well as certain pathologic causes such as gigantism due to pituitary overgrowth and other tumors or congenital deformities. This can be corrected by surgical orthodontic treatment with surgical setback of the mandible.

Other common problems that are associated with the mandible but not due to abnormal growth include broken jaw and Temporomandibular Disorder (TMD).

Broken Jaw

When a bone breaks or cracks the injury is called a fracture. Jaw fractures are the third most common type of facial fractures and can be caused by many different types of impacts to the lower face including:

An accidental fall Hitting the dashboard during a car accident A fall from a motorcycle or bicycle A fall or collision during contact sports A punch to the jaw

The jaw bone is essentially a long bone that includes your chin and angles up toward your ear on both sides of your face. On each side the end of the jawbone is rounded like a ball. This is called the condyle and is part of the jaw joint right in front of your ear that lets you open and close your mouth. This jaw joint is also called the temporomandibular joint (TMJ).

A fracture can happen anywhere along the jawbone but on most cases the jaw fractures in at least two places. Fractures can be classed as �direct� fractures where the jaw was hit or an �indirect� fractures a fracture somewhere else along the jaw.

Fractures of the condyles are the most common type of jaw fractures in children. They usually occur when a child falls and strikes his or her chin against the ground or some other hard surface.

Symptoms of a broken jaw can include:

Bruising swelling and tenderness along your jaw or below your ear Improperly aligned teeth Missing teeth or loose teeth Swelling or a black-and-blue area in the gum over your jawbone Difficulty opening your mouth Pain in your jaw joint Numbness in your lower lip or chin.

A doctor will treat a fractured jaw by either realigning the fractured pieces of bone with wires or by repairing the break with metal plates and fine screws. If any fragments of bone have pieced the skin or if any teeth were lost or loosened your doctor will prescribe an antibiotic usually penicillin to reduce the risk of infection.

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