Mandibular prognathism: what is it and how is it corrected?

Mandibular prognathism is a problem that affects oral functions and the appearance of the face. We tell you what it is and how to correct it.

Last update: May 16, 2022

There are various situations and disorders that can affect people’s bite and the harmony of their smile and face. Mandibular prognathism is one of these alterations. What does it consist of? What are its main causes?

It is a condition that It is characterized by the presence of a lower jaw that is too large or advanced with respect to the upper jaw. The mandible protrudes and affects occlusion and facial aesthetics. We tell you more about it.

What is mandibular prognathism?

The word “prognathism” comes from the Greek “pro”which means “forward”, and “gnathos”, which means “jaw”. This disorder is also known as “skeletal class III malocclusion.”

As we already told you, it is the extension or protrusion of the lower jaw forward. this overtaking causes the chin to protrude excessively and noticeably on the face. This is often due to excessive growth of the lower jaw.

However, it can also be caused by the lack of development of the superior bone that is located far behind. Thus, the upper and lower teeth cannot be properly related.

To diagnose mandibular prognathism, the dentist suggests tests such as dental x-rays.

Causes of mandibular prognathism

The most common origin of mandibular prognathism is usually genetic and hereditary. It is common for people who are born with a larger lower jaw have relatives with the same problem.

Therefore, if there is a history in the family, it is important to take children to the dentist and orthodontist from an early age. In this way, it will be possible to detect the problem to address it early.

In any case, there are external situations that can favor the appearance of this condition. Premature loss of baby teeth is an example. Tonsil or adenoid hypertrophy and mouth breathing are other factors that increase the chances of prognathism.

Sometimes, it can also be a symptom of other systemic diseases. Acromegaly, for example, is a disorder in which there is excessive production of growth hormone and the jaw is often larger.

Patients with Down syndrome and other rarer disorders, such as Crouzon syndrome, nevus and conditions such as acrodysostosis, also present with mandibular prognathism.


The most notable feature of mandibular prognathism is the protruding chin. But this disorder generates several more symptoms, such as the following:

  • Malocclusion: the incorrect relationship of the jaws with each other affects the bite and the position of the teeth in the mouth. The teeth of the lower arch close outside and in front of the upper ones. Sometimes an open bite can be generated, when the patient is unable to occlude.
  • Alteration of oral functions: the patient with mandibular prognathism has problems when biting, chewing, eating and speaking. Diction problems, such as a lisp, tend to be common.
  • Problems in the temporomandibular joint.
  • Frequent headaches.
  • Aesthetic problems: the pronounced chin can mean an aesthetic inconvenience for some people who do not feel comfortable with their appearance. This can lead to feelings of insecurity, low self-esteem and difficulties in relationships.

How is mandibular prognathism diagnosed?

The diagnosis of mandibular prognathism is usually suspected by the dentist and confirmed by the orthodontist. When the general dentist discovers signs of this condition, makes the timely referral to the specialist to resolve the problem.

The physical examination and data from the clinical history —such as family history and certain oral habits— become important when arriving at the diagnosis. But in addition, other resources are necessary to help the professional confirm it.

Dental and skull radiographs, such as orthopantomography and cephalometrics, help to study the problem. Intra and extra oral photographs also provide valuable information.

Bite impressions and obtaining a study plaster model complete the diagnostic process. From this, the professional can plan the most appropriate treatment for each particular patient.

If mandibular prognathism is caused by an underlying medical condition, the dentist may suggest timely treatment for that condition with the right specialist.

How is your treatment?

Therapeutic alternatives when dealing with a skeletal class III occlusion problem depend on the age of the patient. Treating it in a child or adolescent —whose bones have not finished growing yet— is not the same as treating it in an adult who has already completed this training process.

When the treatment is carried out during childhood, it is less invasive and more conservative. In addition, it prevents the symptoms of this disease and its functional, aesthetic and psychological effects from being prolonged over time.

For this reason, it is recommended to take children to the pediatric dentist from the first year of life and see an orthodontist between the ages of 6 and 7, or earlier if suggested by the dentist, for an evaluation of the bite.

Starting treatment in childhood, as soon as the first signs are detected, is much more beneficial. But you should know that there are also therapeutic alternatives for adults. Below we tell you how the problem is solved in both age groups.

Treatment of mandibular prognathism in children

During childhood and adolescence it is possible to correct the increased growth of the jaws. At this stage you can take advantage of the fact that bone formation is still active. This promotes the advancement of the upper jaw or slows down the advancement of the lower jaw in search of a harmonic relationship.

For this, interceptive orthodontics is used, a procedure that acts on the growth of the bone bases at very early ages. In the case of mandibular prognathism, expander devices are used to stimulate the development of the upper jaw.

Also chin guards and orthodontic masks that slow down the growth of the jaw. Once these procedures are done, it may be necessary to supplement with corrective orthodontic treatment to improve tooth alignment. When the bones have the proper position, the malpositions of the teeth are corrected to achieve a good bite.

Treatment of mandibular prognathism in adult patients

In the case of adult patients, in whom bone growth has already finished and mandibular prognathism has already been established, therapy is more complex. If this is your case, you should not be discouraged because it is possible to achieve good results.

In mild cases, you can opt for orthodontic treatment to correct the misalignment of the teeth. This can improve the bite, the appearance of the smile and the relationship of the elements above with those below. However, it does not change the appearance of the face and is not always indicated.

In more serious situations, when functional and aesthetic problems are very evident, it is necessary to combine orthodontic treatment with orthognathic surgery.

The latter is a type of maxillofacial surgery that allows to recover the symmetry and harmony of the face by placing the maxillary bones in their place.

Orthognathic surgery to correct mandibular prognathism

Before submitting the patient to such an intervention, it is necessary to carry out different morphological and aesthetic studies with radiographs and photographs. This helps to plan, to consider the aspects that must be corrected and to determine the most appropriate techniques.

In addition, it allows the patient to be shown the possible result, which makes it easier for them to accept the change and resolve the associated doubts and fears before the procedure. In any case, prior to this, it is necessary to wear orthodontics for a while.

With this, the oral situation becomes more favorable for the intervention. In particular, the dental pieces are positioned in the most convenient areas.

The surgery is performed in an operating room and under general anesthesia, which requires hospitalization. It is in charge of a multidisciplinary team, in which the maxillofacial surgeon plays a primary role. The duration of the procedure can take around 2 hours, although this depends on the complexity of the case.

The process is done through the oral cavity, so there will be no visible scar on the face. Depending on the type of mandibular prognathism of the patient, the upper jaw, the lower jaw or both bones will be mobilized.

The surgeon performs an osteotomy of the maxilla, which consists of fracturing it and placing it backwards. If necessary, excess bone is removed. And to keep the two bone fragments together, they are fixed with titanium plates and nails.

This type of surgery It is only possible to perform it once the patient’s growth has finished. For girls, this usually happens around the age of 16; in children, between 17 and 18. However, this depends on each individual person.

Corrective surgery improves facial aesthetics in patients with mandibular prognathism.

What happens after corrective jaw surgery?

after surgery it is necessary to follow certain care to favor the recovery of the tissues and avoid complications. It will be necessary to follow a liquid and then a soft diet to avoid moving the jaw while it heals.

The surgeon will prescribe medication for pain and to prevent infection. It will also suggest rest for 1 to 3 weeks. It will not be convenient to make efforts, exercises or smoke.

Once the recovery time has passed, orthodontics may need to be worn again for a period. With the appliances, the dental pieces can be positioned in the appropriate location to achieve the desired smile.

Can prognathism be prevented?

When mandibular prognathism is due to hereditary or genetic issues, or is part of a syndrome, it is not possible to prevent it. But it is possible to act on the external factors that favor the appearance of this disorder.

Parents, for example, play a fundamental role in caring for children’s mouths and thus prevent the loss of milk pieces prematurely. Detect and control harmful habits (such as mouth breathing) and looking for a solution in time is also part of prevention.

Dental consultations from an early and frequent age also allow any problem in the mouth to be detected in time; even when everything seems to be going well. Going to the dentist is a simple action, but at the same time fundamental, when it comes to avoiding major problems in the future.

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