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What Is Mandibular Prognathism?

By Andy Josiah
Updated Mar 03, 2024
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Mandibular prognathism is a condition in which the lower jaw protrudes ahead of the upper jaw. This results in an extended chin. Mandibular prognathism affects humans, but also occurs in certain dog breeds such as boxers and shih tzus. The disorder is also known as progenism.

The condition is named for the mandible, which is the medical term for the lower jaw, or jawbone. While the maxilla refers to the two-bone fusion that creates the upper jaw and secures the upper row of teeth, the mandible is one unit that keeps the lower teeth in place. Mandibular prognathism causes a misalignment of the teeth, a condition known as malocclusion. It also lends a certain disfigurement to the face. Mandibular prognathism usually happens when the condylar head, which is the part of the posterior projection of the mandible known as the condyloid process, grows excessively, with the maxilla unable to catch up.

Mandibular prognathism is classified as a genetic disorder. It is sometimes known as the Habsburg jaw, the Habsburg lip or the Austrian lip, after a famous family identified with the condition. The Habsburgs were an aristocratic royal house that ruled a large portion of the known world in the forms of the Holy Roman Empire, Austrian Empire and Spanish Empire for about six centuries. Family members were believed to have developed this deformity due to dynasty-sustaining intermarriage and inbreeding.

Historians point to Maximilian I as the first recorded Habsburg ruler to bear this disorder. A famous member of this family with mandibular prognathism is Charles I of Spain, otherwise known as Charles V of the Holy Roman Empire. The most severe recorded case of mandibular prognathism in the family’s history, however, was of Charles II of Spain; his condition was so severe that he could barely chew his food.

In such a dramatic case, a modern-day person would likely undergo surgery. Referred to as orthognatic surgery, or ramus osteotomy, which is named for the border of the bone that articulates with the condylar head, the procedure requires a dental surgeon to remove part of the mandible. This is meant to realign the jawbone, and items such as screws and plates may be introduced for enforcement of that purpose. Dental surgeons usually work with orthodontists who will recommend braces to align the teeth prior to the surgery. With the combination of braces and surgery, a perfectly aligned jaw and rows of teeth can be achieved.

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Discussion Comments

By anon356297 — On Nov 23, 2013

I'm pretty sure with dogs, it's just as uncomfortable for them as for humans.

By cloudel — On Nov 12, 2011

In humans, an underbite is considered a bad thing. I find it funny that it is considered desirable in a boxer bulldog.

They are definitely odd looking because of their protruding lower jaws. I can't even look at one without giggling. It's as though they are constantly making a funny face, and they can't even help it.

Shih tzus are equally hilarious. They are so little, but they look so fierce because of their serious underbites.

I'm guessing that since people continue to breed these dogs, the underbite must not be painful for them. It looks like it would be uncomfortable in humans, though. Does anyone know if this condition causes pain or if it just feels normal to a person born with it?

By orangey03 — On Nov 12, 2011

@kylee07drg – I had the surgery, and though it was pretty painful for about a week, I got better quickly after that. I'm sure it helped that I had plenty of pain medication.

I had to stay in the hospital for a few days. I got pain medicine intravenously. The nurse kept applying ice packs to my jaws, which she said would help prevent swelling and reduce what was already there.

I stayed doped up for about seven days. They told me to keep my head elevated, even while sleeping. They also said that I should not hesitate to take the pain pills, because this would help me heal faster.

Though it was rough, it wasn't as bad as I expected it to be. If your condition is bothering you a lot, I would recommend jaw surgery. Though I'm sure it will differ in some ways from the type I had, it's in the same area, so you will likely experience a lot of the things I did.

By kylee07drg — On Nov 11, 2011

Has anyone here either had orthognatic surgery themselves or know someone who has? I am just curious, because it sounds like recovery would be extremely painful.

I have frequently had issues with my jaws, though I don't have this condition. Sometimes, when I open my mouth wide, it gets stuck in this position, and I have to move my lower jaw to one side to force it out.

I have considered having surgery to correct it, but I'm afraid of the pain. It hurts so much when I have pain in my jaws, and I would imagine anyone undergoing a surgery as serious as one to correct a malocclusion would have to endure agony.

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