The Mandible (Lower Jaw)

erica medical reviewer
Medically Reviewed
by Dr. Erica Anand
Vine Ayaga
Written by
Vine Ayaga
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Evidence Based
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What is the Mandible (Lower Jaw)?

The mandible is also known as the lower jaw. It is the largest and strongest bony structure of the facial skeleton.1 

The mandible holds the lower teeth and is connected to the skull’s temporal bones through the temporomandibular joint (TMJ). 

The TMJ allows you to move your jaw when chewing, eating, talking, or yawning.

The maxilla, on the other hand, is the upper jaw that holds the upper teeth. It is rigidly attached to the cranium and holds important structures needed for speaking, breathing, and eating.

Mandible Anatomy & Structure 

The mandible is a single bone that is symmetrical on both sides. It has a horseshoe-like shape. 

Male mandibles are generally larger than female mandibles. They also have more pronounced muscle attachment points and are somewhat stronger.2

Below are the parts that make up the mandible:

Body

The body of the mandible is a huge, almost rectangular structure that lies parallel or perpendicular to the floor, depending on whether the person is standing or lying flat. 

The chin gets its structure from this part of the bone.

Ramus

The ramus is the vertical part of the jaw that extends cranially from the angle of the mandible (gonial angle). It is the second-largest part of the mandible. 

The gonial angle may range between 110 and 130 degrees depending on age, sex, and race.3

Each ramus consists of the following parts:

  • Head. This is the part that connects with the temporal bone to form the temporomandibular joint (TMJ).
  • Neck. This part supports the head and acts as the point of attachment of jaw muscles known as pterygoid muscles, which attach to the pterygoid fovea.
  • Coronoid process. Site of muscle attachment (temporalis muscle). The primary purpose of this muscle is to generate mandibular movements at the temporomandibular joint.8

Alveolar Process

The alveolar process is probably the most crucial part of the bone since it keeps the teeth in place via a joint process known as gomphosis.4

This part of the mandible extends from the mandibular body and is made up of two bony plates. 

Each side of the mandible has five primary teeth and seven to eight permanent teeth, depending on whether wisdom teeth or third molars emerge.

Mandibular Foramen

The mandibular foramen is a bony canal found on the internal surface of the ramus. 

This mandibular canal acts as a passage for the inferior alveolar nerve, inferior alveolar artery, and veins which exit at the mental foramen. 

The mental foramen is located at the external surface of the mandibular body between the first and second premolar.

What are the Primary Functions of the Mandible?

The mandible, like the upper jaw or maxilla, has an important structural and protective role. 

This bone houses the bottom set of teeth and contains vital nerves and muscles that travel through it and emerge from it.

The mandible is primarily involved in moving the jaw during activities such as chewing or talking. 

What Problems Can Affect the Lower Jaw?

The lower jaw is prone to disorders and diseases that may reduce its function. These include:

Jaw Fractures

Mandibular fractures may occur due to trauma to the face. These are common during accidents, sports injuries, and assaults. 

Jaw fractures are characterized by pain that worsens when chewing, talking, or moving the jaw up and down. 

Treatment options include:

  • Antibiotic therapy. If the mandibular fracture results from gum problems or tissue damage, your doctor will consider it an open wound prone to infection.
  • Manual repositioning. This involves wiring the upper and lower jaw through manual manipulation.
  • Barton bandage. Your doctor will wrap a bandage running from below the jaw to the backside of your head.
  • Surgery. A badly fractured jaw may require surgery to fix some affected areas.

Jaw Misalignment

Trauma to the face can cause jaw misalignment.5 The consequence of this is crooked teeth. Crooked teeth may also result if trauma to the face leads to tooth loss. 

In this case, if the tooth growth is not managed properly,the growing teeth may shift into the toothless gaps. This contributes to crooked teeth.

Dental issues such as cavities or gum disease may also cause misaligned or uneven jaws. Some people are also born with misaligned jaws, while others acquire it. 

The pain and discomfort of a misaligned jaw can be severe. It may also lead to other health problems. It is critical to get it checked as soon as possible.

Treatment options include:

  • Physical therapy
  • Wearing fixed or removable braces to align crooked teeth
  • Surgery for severe cases

Dislocations 

Jaw dislocation is characterized by detachment at the temporomandibular joint. 

Common causes of jaw dislocation are opening the mouth while yawning or vomiting, and during dental procedures. 

The following are symptoms of a dislocated jaw:

  • Misalignment of the maxilla and mandibular
  • Stiffness or difficulty moving the mouth
  • Inability to close the mouth
  • Underbite or overbite

Treatment options include:

  • Manual repositioning of the mandibles
  • Use of Barton bandage to support the jaw as it heals
  • Surgery in severe cases (such as when ligaments require reduction)

Temporomandibular Joint Disorders (TMD)

TMD is a disorder that affects the jaw and the facial muscles that control its movements. It may occur due to whiplash (neck injury), clenching of the teeth, and arthritis of the joints.6

Treatment options include:

  • Medications or pain relievers
  • Stress management and relaxation techniques
  • Physical therapy
  • Wearing a mouth guard to prevent teeth grinding 
  • Behavioral changes (to stop teeth clenching)
  • Resting the temporomandibular joint (TMJ)
  • Posture training
  • Surgery for severe cases
  • TENS therapy 

Sleep Apnea

Sleep apnea and TMD are two conditions that may coexist and reinforce one another. 

Sleep breathing disorders such as snoring or sleep apnea affect approximately 75% of people with TMD.

On the other hand, TMD affects about 52% of people with sleep apnea. Understanding the relationship between the two conditions is necessary for effective treatment.

Treatment options include:

  • Lifestyle changes for mild cases (e.g., losing weight).
  • Surgery. This may include tissue removal, nerve stimulation, jaw repositioning, or tracheostomy (creating a new airway).
  • Continuous positive airway pressure (CPAP). A machine is used to deliver pressurized air into the throat to keep it open. This prevents snoring and further apnea.7
  • Oral appliances. These are designed to keep the throat open, just like in the case of CPAP.

Osteomyelitis and Bone Disintegration (Rare)

This illness is caused by bacteria entering the body through poor dental hygiene or oral procedures like a root canal. It can also happen after a jaw fracture.

Osteomyelitis in the jaw is more prevalent in males than in women. It occurs more often in the mandible than in the maxilla (bone where the top teeth are arranged). 

People who have diabetes, alcoholism, or other illnesses that affect the immune system are more vulnerable.

Symptoms of osteomyelitis include:

  • Tenderness to touch
  • Tooth loss
  • Fatigue
  • Fever
  • Stiff jaws
  • Headache
  • Neck ache
  • Sinus drainage

During the acute stage of osteomyelitis, you will have growing, persistent jaw pain and sinus pressure that is unaffected by jaw movement. 

If you have chronic osteomyelitis, you may have jaw and neck pain, as well as difficulties eating and speaking.

Treatment options include:

  • Drainage. A procedure known as needle aspiration is used to drain the open wound
  • Antibiotic treatment. This helps get rid of the harmful bacteria
  • Surgery. This is done to scrape out the damaged bone

Resources

The mandible and its features,”3D4Medical, 4 August 2020

Sex Determination of Human Mandible Using Metrical Parameters,” National Center for Biotechnology Information (NCBI), 15 December 2013

Analysis of gonial angle in relation to age, gender, and dentition status by radiological and anthropometric methods,” National Center for Biotechnology Information (NCBI)

Alveolar Process,” International Congress of Oral Implatologists

Misaligned teeth and jaws: Overview,” National Center for Biotechnology Information (NCBI), 16 January 2020

Temporomandibular Disorder (TMD),” John Hopkins Medicine

“Sleep apnea,” Mayo Foundation for Medical Education and Research (MFMER), 18 July 2020

Anatomy, Head and Neck, Mastication Muscles,” National Center for Biotechnology Information (NCBI), 18 June 2021

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