Jawbones play an important role in your face’s shape and appearance. The maxilla, an important bone in the middle of the face, forms the upper jaw.¹ The mandible, the largest bone in the human skull, forms the lower jaw and provides shape to the lower third of the face.² When the jaw alignments are proper, overall health and hygiene are maintained.

Did you know that your jaw size and alignment can impact your health and well-being? Yes, you read it right! Abnormal or protruded jaws can impact your teeth alignment, and oral health, and can cause speech problems.

What is Prognathism?

The term ‘Prognathism’ refers to the protrusion of the upper jaw (maxillary prognathism) lower jaw (mandibular prognathism) or both (bimaxillary prognathism). Prognathism results when the facial bone growth is abnormal. Though genetics play an important role, there are many factors that may lead to protruded jaws. So, it is important to understand the underlying causes and symptoms associated with it.

Types of Prognathism

Maxillary prognathism

In this condition, the upper jaw protrudes further than the normal.

Mandibular prognathism

Prognathism commonly involves the lower jaw and mandibular prognathism is characterised by the abnormal forward projection of the lower jaw.

Bimaxillary prognathism

Both the upper and lower jaws protrude.

Importance of understanding causes and symptoms

The protrusion of the jaw may be normally inherited from parents to their offspring but sometimes it may be associated with other syndromes or hormonal imbalances resulting in excessive growth of jaws.³ So, it is important to understand the underlying medical condition to seek medical attention promptly. Sometimes prognathism can lead to abnormal teeth alignment (malocclusion) which causes difficulty in eating and talking and jaw pain. It is time for a person to get medical intervention from dentists or orthodontists to treat prognathism if they suffer from any of these symptoms.

Causes of prognathism

Genetic factors

• Hereditary influence

The most common cause of protruded jaws is genetics. It can be simply inherited from the parents and there are no sexual preferences. Mostly seen among offspring of affected parents and relatives of affected probands.⁴

• Racial and ethnic predisposition

Research shows that mandibular prognathism is predominantly seen among Asian populations (Highest among Chinese, Korean, and Japanese people) than Caucasians.⁴

Environmental factors⁸

There are many environmental factors that can lead to prognathism of the jaw it includes,

• Enlarged tonsils
• Nasal breathing difficulties
• Improper Posture
• Habitual position of head
• Trauma
• Damage due to Instrumental deliveries

Developmental factors

Prognathism can be because of the underlying medical conditions affecting the growth of jawbones.

• Acromegaly

It is characterised by excessive production of human growth hormone from the pituitary gland. The patients may present with abnormal facial structures including oversized jaw.³

• Gorlin goltz syndrome

Also known as Basal Cell Nevus syndrome. A prolonged chin is seen in the affected patients along with other skeletal abnormalities, jaw cysts and multiple basal cell carcinoma.⁵

• Crouzon syndrome

It is a genetic disorder causing craniofacial malformations associated with bulging of eyes, underdeveloped maxillary bone and severe mandibular prognathism.⁶

• Acrodysostosis

Refers to a group of genetic bone disorders presented with short fingers and toes, short stature, and underdeveloped facial bones.⁷

Symptoms of prognathism

• Change in facial characteristics⁸
  • Protrusion of upper or lower jaws 
  • Thickened lower lip
  • Misshapen nose
  • Flat face
• Skeletal malocclusion
• Impaired speech
• Temporomandibular joint pain
• Difficulty in eating
• Bruxism
• Tooth overbite or underbite
• Difficulty in breathing³

Interesting facts

Long-face syndrome

People with mandibular prognathism often have elongated lower faces which is commonly called ‘long-face syndrome.’ They may also have improper lip closure and open bite in the front tooth region.

Habsburg jaw

The Habsburgs, one of the foremost royal families in Europe, are well known not only for their leadership and intelligence but also, they representing an inheritance pattern of protruding chin. Mandibular prognathism is seen in 23 successive generations of his family and then the term ‘Habsburg jaw’ was coined to denote this condition.

Other names – Undershot jaw, Bulldog jaw.

Autosomal dominant prognathism

A rare, genetic, developmental defect that occurs during the formation of embryos.⁷ It is characterised by forward projection of the lower jaw and open bite. These symptoms may begin to appear at the newborn stage itself.

FAQ’s

What are the other names for mandibular prognathism?

• Long-face syndrome
• Habsburg jaw
• Undershot jaw
• Bulldog jaw

What are the common concerns associated with prognathism?

• Esthetic Concerns - Long narrow face, malocclusion.
• Functional Concerns - Difficulty in chewing, speech, and breathing
• Psychological Problems - Anxiety and low self-esteem because of facial deformity

Summary

Prognathism is a condition characterised by the protrusion of either the upper jaw (maxillary prognathism), lower jaw (mandibular prognathism), or both (bimaxillary prognathism), often resulting from abnormal facial bone growth. Causes include genetic factors, environmental influences, and developmental conditions like acromegaly or syndromes such as Gorlin-Goltz Syndrome and Crouzon Syndrome. Symptoms associated are changes in facial appearance, skeletal malocclusion, impaired speech, difficulty in chewing and temporomandibular joint pain. Treatment may involve medical intervention from dentists or orthodontists.