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Updated on December 16, 2022
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Prognathism: Causes, Symptoms, and Treatment

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What is Prognathism?

Prognathism refers to the protrusion of the jaw relative to the rest of the face. This can affect the mandible (lower jaw), maxilla (upper jaw), or both. When it involves the mandible, prognathism may be referred to as an extended chin or Habsburg jaw.

Jaw shape varies from person to person, and some degree of prognathism may not cause any problems. But some cases are notably disfiguring and can affect quality of life. 

Prognathism is often treated with a combination of orthodontics (to straighten teeth) and orthognathic surgery (to bring the jaw itself into alignment).

A protruding jaw can be a hereditary feature passed down from parent to child. Several rare genetic syndromes can also include prognathism as one characteristic. 

Types of Prognathism

There are several types of prognathism:

Mandibular Prognathism

Mandibular prognathism affects the lower jaw, causing a protruding chin and often an underbite. This is often an inherited trait, and families with a long history of inbreeding may have an increased risk. However, some rare genetic conditions can cause it as well.

Maxillary Prognathism

Maxillary prognathism affects the upper jaw, causing it to protrude further out than the chin and upper face.

Sometimes other conditions can cause the appearance of a protruding upper jaw. These include:

  • Mandibular micrognathism — the lower jaw is abnormally small
  • Mandibular retrognathism — where the lower jaw is set further back than normal

Alveolar prognathism is a more common form of maxillary prognathism. In this condition, the part of the upper jaw that protrudes is the alveolar ridge, where the teeth are rooted.

Thumb sucking and tongue thrusting during childhood can cause this form of prognathism. The upper front teeth will jut forward rather than straight down due to years of pressure from the thumb or tongue.

Bimaxillary Prognathism

Bimaxillary prognathism affects both the mandible and the maxilla. It causes the front teeth and lips to come forward and is associated with an open bite. Like mandibular prognathism, this condition is often genetic.

What Causes Prognathism?

Prognathism is often simply an inherited trait that people are born with. Multiple genes (and epigenetic factors) are thought to be involved.1, 2, 3

While protruding jaws can be found worldwide, some populations are more likely to have certain kinds of prognathism.4 For example:

  • In some European noble families, mandibular prognathism has been linked to one rare gene.2 This is due to successive inbreeding in these families.
  • Asian populations may have a higher prevalence of mandibular or bimaxillary prognathism than European populations.5, 6

Environmental (non-genetic) factors can also play a role. Alveolar prognathism specifically is associated with childhood habits, such as thumb sucking, which can cause an open bite or crossbite to develop.7

However, there are also rare genetic conditions that can include prognathism as a symptom:

Acromegaly and Gigantism

Acromegaly is a condition that occurs when the body begins to produce too much growth hormone. This causes the body’s tissues (including bones such as the jaw) to enlarge beyond their normal limits.8

Gigantism is a similar condition. However, it begins during childhood, causing a person to become significantly taller than average. In contrast, acromegaly affects adults who have already developed, so they don’t become any taller.

In people with acromegaly or gigantism, the excess growth hormone can lead to exaggerated facial features, including prognathism. The lower jaw ultimately sticks out because it continues to grow beyond where it would otherwise naturally stop.

Basal Cell Nevus Syndrome

Basal cell nevus syndrome, also known as Gorlin syndrome, is a rare hereditary condition that can cause various facial abnormalities. These include a broad nose, far-apart eyes, a heavy brow, and prognathism. It may also cause pitting in the palms of the hands or on the feet.

This condition can cause cysts to appear on the skin and greatly increases the risk of skin and cervical cancers. In some cases, the nervous system and brain are also affected, which can cause intellectual disabilities, blindness, or deafness.9

Talk to your doctor as soon as possible if your child shows signs of basal cell nevus syndrome, such as prognathism, wide-set eyes, and hand or foot pitting.

Acrodysostosis

Acrodysostosis is an extremely rare condition, with just 80 known cases worldwide.10 It can cause shortened limbs, a shortened nose, hearing difficulties, a protruding jaw, and other physical deformities.

Other Genetic Disorders

Some genetic disorders, such as Crouzon syndrome and Down syndrome, can cause the maxilla or midface to be smaller than normal. This can create the appearance of mandibular prognathism.

Symptoms of Prognathism

The symptoms of prognathism vary from person to person. These symptoms may include the following:

  • Protrusion of either the upper or lower jaw (or both)
  • An underbite or an overbite (depending on the type of prognathism)
  • An open bite or crossbite (in cases of alveolar prognathism)
  • Difficulty talking
  • Difficulty eating and chewing
  • Breathing complications, which may cause sleep disturbances

How is Prognathism Diagnosed?

To diagnose prognathism, your doctor will conduct a physical exam. They’ll also ask you about your symptoms, as well as your family and medical history. To get a more complete picture, they will also take X-rays and dental impressions.

Sometimes prognathism is merely one symptom of a much broader syndrome. In cases like these, medical doctors may be able to diagnose the underlying medical condition. The condition may require a wide range of treatments in addition to addressing any complications of prognathism.

How is Prognathism Treated?

Some degree of prognathism isn’t always a problem. It may not significantly impact someone’s ability to talk, eat, or breathe properly. In these cases, prognathism may only pose a cosmetic concern, if any concern at all. 

Prognathism can affect a person’s day-to-day life if it makes talking, eating, or breathing difficult, or if the cosmetic impact is severe. Fortunately, prognathism can be treated in a variety of ways. This generally includes both orthodontics and surgery:

Orthodontic Treatment

Your orthodontist or dentist may be able to diagnose your or your child’s prognathism and perform orthodontic treatment to help correct the bite. This may include braces, palate expanders, and other orthodontic devices.

In many cases, an orthodontist works with an oral surgeon. This is because optimal results may not be possible with orthodontic treatment alone. By combining the two kinds of treatment, a complete realignment of the teeth and jaw can be achieved.

If you or your child have prognathism, talk to your health and/or dental care provider about your treatment options.

Orthognathic Surgery

Orthognathic surgery is performed to correct the alignment of the jaw. While orthodontic treatment can straighten teeth, severe jaw misalignments often require surgical intervention to correct. 

This type of surgery is performed by an oral and maxillofacial surgeon who specializes in treating the bone structures of the mouth and face.

Recovering After Corrective Jaw Surgery

It takes about 9 to 12 months to fully recover from corrective jaw surgery. During this time, you’ll need to follow your surgeon’s instructions to make recovery as efficient and complication-free as possible.

You’ll eat a modified diet as directed by your surgeon for at least the first few weeks while your jaw heals. You may be able to return to work and routine tasks after 2 to 3 weeks.

The exact recovery needs and timeline will differ from person to person. They may be affected by your age, as well as the underlying condition responsible for your jaw issues.

Can Prognathism Cause Teeth Misalignment?

Yes, prognathism can cause your teeth to shift out of alignment. This is called malocclusion, which can make chewing, biting, and talking more difficult. It can also lead to oral health problems, as crooked teeth are harder to clean.

Orthodontic treatment, such as clear aligners or traditional metal braces, can help fix these issues. But if your jaw is severely misaligned, this treatment may need to be combined with orthognathic surgery. Talk with your dentist about options.

Can You Prevent Prognathism?

Unfortunately, you cannot prevent prognathism that is caused by genetic conditions. A protruding jaw may just be part of a person’s appearance and may not pose any problems.

However, you can prevent changes in jaw shape caused by teeth misalignment. Curbing habits like thumb sucking in your child can prevent them from developing alveolar prognathism. Early orthodontic treatment can also correct misaligned teeth before the problem becomes more severe.

Prognathism that already exists can be treated if it causes problems.

Outlook

Prognathism can refer to a wide range of jaw conditions. Some are mild and may not cause any issues beyond mild cosmetic concerns. Others may need extensive treatment to make day-to-day life easier.

Because a wide range of orthodontic and surgical options are available, people with prognathism can benefit from comprehensive treatment plans. Both dental alignment issues and underlying skeletal (jawbone) problems can be addressed.

Many people have had their jaw issues corrected with the right treatment and no longer experience discomfort or trouble with daily activities. Your doctor or dentist can help you determine what treatment options are best for you or your child.

Summary

Prognathism refers to a protruding upper and/or lower jaw. It may involve severe malocclusion of the teeth, and cause problems with eating, speaking, and breathing. Other cases may be mild and present minor or no issues.

The underlying causes of prognathism are largely genetic, and sometimes it comes along with other symptoms as part of a broader medical condition.

Treatment for prognathism often involves a combination of orthodontic treatment and corrective surgery. Talk to your doctor if you or your child experience difficulty in day-to-day life due to jaw misalignment.

Last updated on December 16, 2022
13 Sources Cited
Last updated on December 16, 2022
All NewMouth content is medically reviewed and fact-checked by a licensed dentist or orthodontist to ensure the information is factual, current, and relevant.

We have strict sourcing guidelines and only cite from current scientific research, such as scholarly articles, dentistry textbooks, government agencies, and medical journals. This also includes information provided by the American Dental Association (ADA), the American Association of Orthodontics (AAO), and the American Academy of Pediatrics (AAP).
  1. Sun, R., et al. "Identification and Functional Studies of MYO1H for Mandibular Prognathism." Journal of Dental Research, 2018.
  2. Wolff, G., et al. “On the genetics of mandibular prognathism: analysis of large European noble families.” Journal of medical genetics, 1993.
  3. Zabrina, Stephanie, et al. "Genetic and epigenetic aspects of class III malocclusion with mandibular prognathism phenotypes." AIP Conference Proceedings, 2021.
  4. Hoyte, Trudee, et al. "Prevalence of Bimaxillary Protrusion: A Systematic Review." Open Journal of Epidemiology, 2021.
  5. Chu, Yong-Ming, et al. “Bimaxillary protrusion: an overview of the surgical-orthodontic treatment.” Seminars in plastic surgery, 2009.
  6. Payne, Jacqueline, and Marie Tolarova. "Genes Associated with Mandibular Prognathism in the Chinese Population." Dugoni School of Dentistry, 2018.
  7. Tanaka, Orlando, et al. "Breaking the Thumb Sucking Habit: When Compliance Is Essential." Case Reports in Dentistry, 2016.
  8. Acromegaly.” Genetic and Rare Diseases Information Center.
  9. Basal Cell Nevus Syndrome (Gorlin Syndrome).” Johns Hopkins Medicine.
  10. "Acrodysostosis." Orphanet.
  11. Mani, Varghese. "Orthognathic Surgery for Mandible." Oral and Maxillofacial Surgery for the Clinician, Springer, 2021.
  12. Möhlhenreich, Stephan Christian, et al. "Effects of different surgical techniques and displacement distances on the soft tissue profile via orthodontic-orthognathic treatment of class II and class III malocclusions." Head & Face Medicine, 2021.
  13. Kahn, Sandra, et al. “The Jaw Epidemic: Recognition, Origins, Cures, and Prevention.” Bioscience, 2020.
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