What to Know About Prognathism

What to Know About Prognathism?

Prognathism is a condition caused by a defect in the jaw bones (mandible and maxilla). There are two types of prognathisms: maxillary and mandibular. Maxillary prognathism occurs when one or both of these teeth are missing. Mandibular prognathism happens when only one tooth is missing.

Mandibular prognathism is rare. However, it does occur in some cases. For example, if the mandible is broken and there is no bone between the upper and lower jaws, then the patient will have a maxillary prognathism. If one or both of these teeth are missing, then the patient will have a mandibular prognathism.

The main causes of maxillary prognathisis include trauma (e.g., being hit by a car), disease, injury, and dental problems such as abscesses. A few other possible causes include congenital defects (such as cleft palate) and tumors.

Maxillary prognathisis usually affects males more than females. Most patients with maxillary prognathisis develop symptoms within their teens or twenties. The most common symptom is severe pain in the back of the mouth while chewing gum or eating food. Other symptoms include increased pressure in the sinuses, frequent headaches, a change in the patient’s voice (usually deeper), bad breath, and dental problems.

The main causes of mandibular prognathisis include disease and injury. Trauma is not thought to be a major cause of mandibular prognathisis.

The most common symptom of mandibular prognathisis is a misaligned jaw, which may make it difficult to chew food and speak clearly. Some patients experience tooth pain or problems with their bite (the way the upper and lower teeth come together). Many patients with this condition have impacted wisdom teeth. A few patients also develop pain or swelling in the temporomandibular joints (joints at the top and bottom of the jaw).

Types of Prognathism

There are two types of prognathism: mandibular and maxillary. The type depends on which of the jaw bones is affected.

Prognathism is more common in males. It usually develops between the ages of 5 and 15. It affects people of all races. The condition is usually genetic, but sometimes it is caused by an inherited connective tissue disorder.

Some doctors use different names for some types of prognathism. The types described below are the most commonly used terms.

Prognathism Symptoms

The symptoms of prognathism depend on which jaw bone is affected.

Symptoms of mandibular prognathism may include:

A protruding jaw (lower case)

Difficulty chewing and biting

Teeth that are crooked or don’t come in properly

Chronic sore throat, earaches, and problems with TMJ (temporomandibular joint syndrome)

Difficulty breathing through the nose due to a deviated septum caused by the protruding jaw (lower case)

Difficulty speaking

Chronic allergies or a runny nose

Poorly aligned teeth, which leads to tooth decay and eventual loss of teeth

Speech impediments (stuttering is common)

Difficulty clearing the throat due to the masseter muscle being in the way

Ear infections and pain

Crowded teeth, causing forced closure of the jaw (the upper and lower teeth don’t close in a straight line) and increasing risk of bruxism (chewing on the wrong part of the jaw)

Stomach pain

One or both sides of the face may be affected

Symptoms of maxillary prognathism may include:

A protruding upper jaw (lower case)

The top front teeth protrude out in front of bottom teeth.

Diagnosis If any tooth has more than a 3mm difference between it and its adjacent tooth, then it is said to have a Class II malocclusion.

A simple visual inspection by a dentist is usually all that is needed to determine if a misalignment exists. A more accurate measurement can be done using dental casts and a sliding rule called an occlusal plane disc (OP disc) available from most dental suppliers. The OP disc has the ability to measure a particular tooth and its opposite tooth on the other side of the jaw for their exact alignment in reference to one another.

A radiograph, or x-ray, is required to assess the actual bone structure of the upper and lower jaw. This will give a clearer indication if a prognathic condition exists and to what degree it exists.


The treatment of prognathism depends on the cause, type and the severity of the condition. Most patients with this condition find relief through a combination of orthodontic treatment (braces) and surgery.

Orthodontic Treatment

Your dentist will first rule out any potential problems, such as infections or other medical conditions. If all appears to be normal, then he/she may suggest a retainer at nighttime to keep your jaw from slipping back to its original position while you sleep.

Your dentist may also suggest or arrange for you to see an orthodontist (a specialist in correcting the alignment of teeth and jaws) who can provide a more permanent solution. Several different types of appliances can be used, mainly to move the teeth or the jaw.


Surgery is another option if the above treatments are ineffective or don’t provide enough improvement. The most common surgery is performed on the mandible (lower jaw). The goal of this surgery is to remove part of the bone of the lower jaw and reposition it so that it will no longer protrude.

To learn more about this disorder, please see your local dentist or search the web for “prognathism.”

What is a mandibular prognathism?

A mandibular prognathism (lower case) is a condition in which the lower jaw protrudes beyond the upper jaw. The lower teeth are often aligned in front of the two upper central incisors.

Because of this, the tongue and lower lip may block the airway when you sleep, causing sleep apnea. This can be very serious and may even lead to death if not treated. In most cases, the cause of this disorder is unknown. It may be more common in patients with a hormonal imbalance, however.

The jaw is normally anchored by muscles, which keep the jawbone in place. In a mandibular prognathism, these muscles are weaker than normal. As a result, the jaw bone is no longer held in place as it should be. Instead, it protrudes or sticks out.

When the lower jaw protrudes excessively, it is called a Class II malocclusion of the jaw. This is a more serious condition. A mandibular prognathism that does not cause an overbite is said to be a Class IIIA malocclusion. A mandibular prognathism that causes an overbite is said to be a Class IIIB malocclusion.

A mandibular prognathism is sometimes referred to as a overbite or less commonly as prognathism or a negative overjet.

It is important to distinguish this condition from a maxillary prognathism, in which the upper jaw protrudes. In most cases, a mandibular prognathism is the cause of an overbite.

Sources & references used in this article:

Some biological aspects of prognathism and occlusion of the teeth by A Björk – Acta Odontologica Scandinavica, 1950 – Taylor & Francis

Stability after surgical correction of mandibular prognathism using the sagittal split ramus osteotomy and fixation with poly-L-lactic acid (PLLA) screws by K Harada, S Enomoto – Journal of oral and maxillofacial surgery, 1997 – Elsevier

Mandibular prognathism by CC Alling – Oral Surgery, Oral Medicine, Oral Pathology, 1961 – Elsevier

Genome scan for locus involved in mandibular prognathism in pedigrees from China by Q Li, F Zhang, X Li, F Chen – PLoS One, 2010 – journals.plos.org

Prognathism, with operative treatment by WM HARSHA – Journal of the American Medical Association, 1912 – jamanetwork.com

Changes in alveolar prognathism and anterior teeth protrusion in Japan by Y Kaifu – Anthropological Science, 1999 – jstage.jst.go.jp

A new approach to the treatment of mandibular prognathism by JK Gold – American journal of orthodontics, 1949 – ajodo.org