Prognathism: Causes, Symptoms, and Treatment

What is Prognathism?

Humans (unlike apes and primates in general) have orthognathic faces. In other words, human faces lie beneath the anterior cranial fossa (which is the area just behind the forehead, holding the front lobes of the brain).

Apes, for example, have prognathic faces that project outward from the anterior cranial fossa. Therefore, prognathism refers to an extension of the lower jaw (the mandible). The jaw protrudes out from the face, so it appears to bulge.

Prognathism

Prognathism is also sometimes referred to as an extended chin or Habsburg jaw. It happens when the teeth are not correctly aligned. The shape of facial bones can cause malocclusion (the misalignment of teeth) and, as such, prognathism. That said, prognathism can also be genetic or caused by an underlying condition.

Mandibular Prognathism vs. Maxillary Prognathism

There are three types of prognathism. Mandibular prognathism happens when the bottom jaw (mandible) extends out from the face further than it should.

Maxillary prognathism (sometimes called alveolar prognathism), on the other hand, occurs when the upper jaw (maxilla) protrudes out from the face. Bimaxillary prognathism happens when both the top and bottom jaw stick out further than the rest of the face.

These conditions may be caused by the misalignment of teeth, a genetic disorder, or an underlying medical condition. Likewise, all of these conditions may be perfectly fine to live with, or they may cause some issues with talking, eating, and breathing. 

What Causes Prognathism?

Misaligned teeth are often the cause of prognathism. The teeth can actually change the shape of the jaw as they grow in. Many people are also born this way. Simply, their faces are structured with a jaw bone that sticks out from the time they are born.

However, in some cases, an underlying condition may be at the root of prognathism. Here are some of the underlying medical conditions that can cause prognathism:

  • Acromegaly — Acromegaly is a condition that occurs when the body produces too much growth hormone, which then causes the body’s tissues to enlarge. In the case of prognathism, the lower jaw ultimately sticks out because it continues to grow after a natural growth pattern stops.
  • Basal Cell Nevus Syndrome — Basal Cell Nevus Syndrome is a rare, hereditary condition that causes facial structure abnormalities. These include a broad nose, far-apart eyes, a heavy brow, and prognathism.
  • Acrodysostosis — Acrodysostosis is an extremely rare condition that some people are just born with. It sometimes causes shortened limbs, a shortened nose, hearing difficulties, a protruding jaw, and other physical variances.
  • Certain Genetic Disorders — Some genetic disorders such as Crouzon Syndrome and Down Syndrome can also cause prognathism. Crouzon Syndrome is caused by the premature fusion of certain skull bones in a process called craniosynostosis. And Down Syndrome (also known as Trisomy 21) refers to a condition in which a person has an extra chromosome, which determines how their body is formed.
  • Teeth Misalignment — crooked and spaced teeth can cause prognathism.

Is It Genetic?

While prognathism is not always passed down, it can be genetic. A family medical history of an unusual jaw shape or an abnormal alignment of the jaw can be behind pediatric prognathism in some cases.

Talk to your doctor or general dentist about your chances of passing down 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)
  • Difficulty talking
  • Difficulty eating and chewing
  • Breathing complications

How is Prognathism Treated?

Prognathism is not always a problem. Sometimes, the symptoms associated with prognathism do not significantly impact someone’s life. Beyond changing the shape of their face, they can still talk, eat, and breathe properly. Prognathism may only pose cosmetic insecurities for them if there are any concerns at all.

In some cases, prognathism does affect a person’s day-to-day living. Fortunately, prognathism can be treated in a variety of ways. Here are some options to treat prognathism if you choose to seek care:

  • Medical Care — There are several medical disorders that can induce the misalignment of the biting surfaces of your mouth. Prognathism can be a symptom of other syndromes. In this case, your doctor may be able to diagnose and treat an underlying medical condition. This will likely start with a physical exam from your primary health care provider. 
  • Orthognathic Surgery — You may choose to visit an oral and maxillofacial surgeon to give you a more normal face shape and change your jaw structure’s appearance if you have prognathism. An oral surgeon can change the shape of the facial bones.
  • Dental/Orthodontic Care — Your orthodontist or dentist may be able to diagnose your prognathism and perform orthodontic treatment to correct your jawline. In many cases, they will work in conjunction with an oral surgeon.  The oral surgeon will likely take diagnostic tests including skull X-rays (panoramic and cephalometric) or X-rays of your lower teeth, the lower lips, and your jaw malformation prior to any treatment plan.

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

What to Do After Corrective Jaw Surgery

It takes about 9 to 12 months to heal from corrective jaw surgery. During this time, you will eat a modified diet directed by your surgeon until your jaw heals (for the first six weeks). You can return to work and daily life after 2 to 3 weeks post-op.

Can Prognathism Cause Teeth Misalignment?

Yes, prognathism can cause your teeth to shift out of alignment. This is referred to as malocclusion, which can make chewing, biting, and talking more difficult. It can also lead to jaw pain and oral health issues like gum disease and cavities (crooked teeth are harder to clean).

Orthodontic treatment such as Invisalign or traditional metal braces can help fix these issues. Talk with your dentist about the options available.

Can You Prevent Prognathism?

Unfortunately, you cannot prevent a case of prognathism that is due to genetic conditions. A protruding jaw may just be part of a person. And it may not be an issue.

You can help prevent the jaw from changing shape by properly aligning your teeth. For example, a dentist or orthodontist may give you braces, a retainer, or a mouthguard to help correct an underbite.

You can also treat prognathism with medical care and/or orthodontic treatment if you already have it. For some people, treatment may be necessary to talk, eat, and breathe properly.

Resources

Center Turó Park Medical. “Prognathism: What Is It and How to Recognize It?” Turó Park Dental & Medical Center, 2 Jan. 2020, turoparkmedical.com/blog/prognathism/.

“Crouzon Syndrome: MedlinePlus Genetics.” MedlinePlus, U.S. National Library of Medicine, 18 Aug. 2020, medlineplus.gov/genetics/condition/crouzon-syndrome/.

“Facts about Down Syndrome.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 5 Dec. 2019, www.cdc.gov/ncbddd/birthdefects/downsyndrome.html

“Multimedia Encyclopedia - Penn State Hershey Medical Center - Penn State Hershey Medical Center.” Penn State Hershey Health Information Library, pennstatehershey.adam.com/content.aspx?productid=117.

“Prognathism: MedlinePlus Medical Encyclopedia.” MedlinePlus, U.S. National Library of Medicine, medlineplus.gov/ency/article/003026.htm.

“What Is Prognathism and How Is It Treated?” Oral Surgeon, www.faceandjawsurgery.com/what-is-prognathism-and-how-is-it-treated/.

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