Prognathism: What is it? Causes, Characteristics, Diagnosis and Treatment

It is a projection or extension forward excessively of the lower jaw, which generates facial features such as disfigurement of the face.

Giving the person an appearance of anger or fighter, there is a misalignment of the bite surface of the upper and lower teeth.

This abnormal disposition of the teeth is called malocclusion class III and is identified because the lower teeth have a bite in front of the upper teeth.

When the prognathism occurs, there is a primary effect in the lower jaw and in the upper jaw and chin side effects.

The degree of deformity will depend on the relationship between the excessive unilateral growth of the condyle, and any additional growth of the other facial bones.

The protruding jaw or extended chin is also called the ” Hapsburg jaw “.

This condition is usually a sign of an underlying condition.


The extended jaw may be a normal feature of the shape of an individual’s face and whose condition is present from birth.

In this case the mandibular prognathism is due to an abnormal development at the time of development and growth of the fetus during pregnancy.

According to the jaw bone that presents the defective extension, the prognathism can be:

  1. Mandibular prognathism: This occurs when the lower jaw extends abnormally forward.
  2. Maxillary prognathism: Occurs when the upper jaw is the one that protrudes.
  3. Bimaxillary prognathism: It is one in which the two jaws project forward more than the rest of the face.

On other occasions prognathism may be associated with some of these underlying conditions:


This condition occurs when the body produces high amounts of growth hormones, which produces an enlargement of the tissues.

The lower jaw protrudes as excessive growth occurs.

Crouzon’s syndrome

The prognathism may have its origin in hereditary conditions, such as Crouzon syndrome whose condition causes a rare facial appearance as wide nose, thick and prominent eyebrows, eyes widely separated and prominent jaw.


This condition of birth is very rare, features such as shortened arms and legs, hearing problems, the presence of a short nose, mental retardation and a prominent jaw may occur.

Although the main reason for prognathism is hereditary, there are other factors that can cause them as environmental factors.

There are a number of factors such as pushing the tongue, frequent nasal congestion, the adoption of an unhealthy technique of mouth breathing, which force the tongue to rest against the lower jaw.

When the lower bite is not treated properly, this can lead to extreme cases and trigger an extended chin and therefore a facial abnormality.


Within the distinguishing characteristics of the prognathism are observed:

The coexistence of class III malocclusion. In Class III cases, mandibular prognathism or increased jaw growth is characterized by the fact that the middle third of the face is normal.

It is observed that the nose and cheekbones have a normal projection, but a predominance is observed in the anteroposterior part of the chin.

The malocclusion is derived from prognathism, this condition affects the bite, can cause problems in speech and chewing.

This malocclusion triggers the irregular location of the teeth, and a deficient smile.

The irregular bite is also caused by the prognathism, which causes a misalignment of the teeth, especially those located at the bottom.

The extreme deep bite hinders oral well-being, begins by affecting swallowing, crushing of food, tears of enamel and speech.

It also makes it susceptible to dental problems, since misaligned teeth are also more difficult to clean, which increases the risk of diseases such as dental caries, temporomandibular disorders and periodontal diseases.

This condition is characterized by incomplete closure of the lip, deviating the midline and causing a reduction of the labiomental fold.

The border of the upper lip is fine or diminished and the lower lip is full and arched outward, below the protruding upper incisor teeth.

This abnormal location of the teeth is associated with significant changes in the appearance of the face, caused by the abnormal growth of the bones.

In cases of little growth of the maxilla, it is very common to find little development of the paranasal area, the base of the constricted nose and a little exposure of the upper incisors when the face is at rest or when it is not smiling.

The minimal development in the area of ​​the malar is characteristic, which gives the impression of a sinking in the middle third of the face.

This facial appearance is best seen when we look at the profile, the chin is not well defined, the incisors are tilted forward.

With this outward projection of the lower part of the face, there is no support for the soft tissues of the cheeks, neck and chin.

This inadequate support is aggravated by the normal aging process.

Mandibular prognathism is detected by:

  • The jaw bone exhibits an abnormal growth by excess with respect to the maxilla, which is known as a skeletal problem.
  • The patient presents a disproportion due to the size of the chin.
  • The prominent jaw is caused by a dental problem, that is, the teeth are misaligned.


It is very important to prepare an adequate diagnosis to later recommend the treatment for the underlying disease.

Correcting the cause of the alteration of growth, orthodontic treatment and facial cosmetic surgery on the bones that are to be corrected.

A physical examination should be performed, emphasizing the medical history in aspects such as family history of an unusual mandibular formation, presence of difficulties in speaking, biting or chewing in addition to the presence of other symptoms.

Tests for differential diagnosis include performing skull and dental x-rays, impressions of the bite.

Any underlying condition causing this condition must be diagnosed.


In general, a careful complementary diagnosis and the planning of an adequate treatment are necessary to correct prognathism.

As a fundamental principle, combined plans of surgical and orthodontic treatment must be carried out.

The three solutions to this problem are:

  1. The orthodontic treatment.
  2. Bimaxillary orthognathic surgery, when surgery is required on the jaw and maxillary bone, or orthognathic monomaxillary surgery, when only one of the two skeletal structures is acting. Probably, orthognathic surgery is accompanied by an additional orthodontic treatment.
  3. Mentoplasty or chin reduction surgery.

The most frequent treatment is the use of orthodontics, this relocates the poorly positioned teeth in the planning of orthodontic treatment should include pre and postoperative orthodontic treatment.

The use of an acrylic dental appliance is recommended to achieve the exact occlusal fit after surgery.

The use of these orthopedic devices induces the teeth to achieve a new position.

Among the equipment currently used are orthopedic devices such as contraction facial masks, orthodontic retainers and expanders of the upper jaw.

Orthodontic therapy allows moving the teeth in the jaw, but the methods involved in oral surgery are more effective and complex.

The option of this method of surgical repair is necessary, to avoid the negative effects of a prognathous jaw.

Regardless of whether the lower bite problems are mild or severe, this problem should be prevented, resolved and addressed as soon as possible.

Surgical treatment in this type of condition eliminates the skeletal defect that is present in the prognathism.

With the practice of surgery, a facial balance is obtained in face deformation and a functional occlusal relation.

The surgeon will remove and reposition the bone parts as required. The jaw will be fixed in the right place with the help of plates, screws or cables.

The solution of mandibular prognathism solves the patient’s functional problems such as the suppression of discomfort when chewing or temporomandibular joint pains.

In addition, once the intervention is done, an aesthetic improvement is also achieved in the softer, more delicate and harmonious facial features.

Treatment of underlying diseases

In the case that the prognathism occurs due to acromegaly, this underlying disease can be treated, performing a surgical removal of the pituitary tumor that causes the excessive production of growth hormone.

You may only need to recommend medications to control the level of the hormone that is released or to block its effects.

In the case of basal cell nevus syndrome, treatment will depend on which parts of the body are being affected.

Treatment after corrective surgery

  • After performing the corrective surgery of the jaw, a soft diet should be followed temporarily.
  • Treatments for pain and rest for one to three weeks will be prescribed.
  • The jaw will require nine to twelve months to heal completely.
  • After the surgery, orthodontic therapies are performed if necessary.
  • Like any other dental disease, it can improve your quality of life, when it is detected at an early stage.
  • Early detection is a possibility to avoid more complex dental procedures.