Prognathism refers to the forward protrusion of the jaw, especially the lower jaw (mandible), beyond the natural alignment with the upper jaw. In simple terms, it means that one or both jaws protrude or “jut out” further than is typical. This skeletal misalignment directly affects how the upper and lower teeth meet, a relationship known as occlusion. When the jaws are not aligned, it often leads to a malocclusion, or “bad bite.”

To understand the functional impact, it is helpful to use an analogy. Think of your upper and lower teeth as two perfectly engineered sets of gears in a complex machine. For these gears to mesh correctly and work efficiently, the framework that holds them, your jaws, must be perfectly aligned. In prognathism, this framework is misaligned. It is as if one of the gear assemblies is positioned too far forward, causing the teeth to meet improperly. This can lead to difficulty chewing, abnormal wear and tear on the teeth, and strain on the jaw joints.

There are three main types of prognathism, each with a distinct appearance and effect on the bite:

• Mandibular Prognathism: This is the most widely recognized type, where the lower jaw (mandible) outgrows the upper jaw and juts forward. This causes the lower teeth to sit in front of the upper teeth when the mouth is closed, creating what is commonly known as an underbite. Medically, this is called a Class III malocclusion.
• Maxillary Prognathism: In this type, the upper jaw (maxilla) protrudes significantly. This can make the upper front teeth and gums very prominent, sometimes leading to a “gummy” smile or difficulty closing the lips together naturally over the teeth. This is often associated with a significant overjet, where the top teeth project far beyond the bottom teeth.
• Bimaxillary Prognathism: This describes a condition where both the upper and lower jaws are positioned forward relative to the rest of the facial structure. In this case, the teeth may align relatively well with each other, but the entire lower face has a protrusive appearance.

In my experience, patients are often more concerned about the cosmetic aspect, but once we discuss its effects on speech and bite, they understand why early evaluation is so important.

In most cases, the cause of prognathism is primarily genetic and hereditary. The size, shape, and growth pattern of our facial bones, including the jaws, are determined by the genetic information we inherit from our parents and ancestors. A particular jaw structure is often a familial trait that is passed down through generations.

In a smaller number of cases, significant prognathism is not just an isolated familial trait but is a key feature of an underlying genetic syndrome that affects craniofacial development. There are several hundred such syndromes, but some of the more well-known ones associated with prognathism include:

• Crouzon syndrome: A genetic disorder characterized by the premature fusion of certain skull and facial bones.
• Apert syndrome: A condition involving widespread abnormalities of the skull, face, hands, and feet.
• Nevoid basal cell carcinoma syndrome (Gorlin syndrome): A hereditary condition that affects many parts of the body and increases the risk of developing certain tumors.

Finally, in very rare instances, prognathism can be an acquired condition that develops later in life. This is almost always due to a hormonal disorder that causes an excess of growth hormone. Acromegaly in adults and pituitary gigantism in children can cause continued and disproportionate growth of the bones, including the mandible, leading to the development of an underbite over time.

Clinically, I always ask about family history, growth patterns, and any past syndromic diagnosis. Prognathism often has deep developmental roots.

Prognathism may be present at birth, develop during childhood, or appear in adolescence as bones mature.The primary risk factors are:

• Family History: This is the strongest predictor. If one or both of your parents or other close relatives have a prominent upper or lower jaw, you have a higher chance of inheriting a similar growth pattern.
• Ancestry: Different ethnic populations around the world have distinct, normal variations in facial structure, including the prominence of the jaws. A particular jaw alignment may be a common feature within a specific ethnic group.
• Having an Associated Genetic Syndrome: Being born with a diagnosed craniofacial syndrome often incorporates prognathism as part of the condition’s profile.

Patients often say, “I just thought I had a strong jawline,” until orthodontic problems or bite issues brought them to medical attention.

The appearance of prognathism can vary in its type and severity. For some, it’s only cosmetic, while for others, it affects speech, eating, and dental health.

The common signs and symptoms associated with prognathism include:

• Malocclusion (Improper Bite): This is the most direct functional result of the skeletal misalignment and is the source of many other symptoms.
• Difficulty with Chewing (Mastication): The inability to bring the teeth together properly can make it difficult to bite into food or chew efficiently.
• Speech Difficulties: The incorrect positioning of the jaws and teeth can interfere with the tongue’s movement and ability to make proper contact, leading to problems with articulating certain sounds, such as a lisp.
• Jaw Pain and TMJ Disorders: The misalignment can place significant stress and strain on the temporomandibular joints (TMJ), the complex joints that connect the jaw to the skull. This can lead to chronic jaw pain, headaches, and clicking or popping sounds in the joint.
• Abnormal Tooth Wear: A misaligned bite can cause certain teeth to bear more force than they are designed for, leading to excessive and uneven wear, chipping, or fractures over time.
• Mouth Breathing and Lip Incompetence: In cases of severe prognathism, it may be difficult to comfortably seal the lips together at rest. This can lead to habitual mouth breathing, which can cause dry mouth and increase the risk of dental cavities and gum disease.

Clinically, I’ve seen teens experience social anxiety linked to jaw appearance, but after correction, both function and confidence improve drastically.

Diagnosis is usually made through clinical examination and imaging, often during dental or orthodontic evaluations. The diagnostic process involves several key steps to precisely identify and quantify the nature of the jaw misalignment:

• Physical Examination: A specialist will carefully assess the patient’s facial profile from the front and the side. They will examine the bite, measure the degree of overbite or underbite, and evaluate the function of the jaw during opening and closing.
• Dental Impressions or Scans: Models of the teeth are created, either from physical putty impressions or with a digital intraoral scanner. These models allow detailed, three-dimensional analysis of the bite relationship.
• Specialized Radiographs (X-rays): Imaging is essential for evaluating the underlying skeletal structure.
  • A cephalometric X-ray, which is a standardized profile X-ray of the skull, is the most important imaging tool. It allows the orthodontist to perform a detailed analysis, taking precise measurements of the angles and positions of the jaws relative to the skull base and to each other.
  • A panoramic X-ray provides a broad, two-dimensional overview of all the teeth, the upper and lower jaws, and the TMJ.
• Photographs: A series of clinical photographs of the face and teeth are taken to document the facial aesthetics and bite before treatment.

Treatment depends on the severity, age, and cause of the prognathism. For mild cases with no significant functional problems, no treatment may be necessary. For more significant skeletal misalignments, the standard of care is a carefully sequenced combination of orthodontics and surgery.

The Collaborative Team Approach

Successful prognathism treatment requires a close partnership between an orthodontist and an oral and maxillofacial surgeon.

1. Orthodontics (Braces): In most surgical cases, orthodontics is the essential first phase of treatment.

• Pre-Surgical Orthodontics: The patient will typically wear braces for a period of 12 to 18 months before the surgery. The goal of this phase is not to fix the bite, but rather to straighten and align the teeth properly within each individual jaw. This process removes any dental compensations the body has made and moves the teeth into the ideal position they will need to be in after the jaws have been surgically realigned. This can temporarily make the bite look and feel worse, which is a normal and necessary part of the process.

2. Orthognathic (Corrective Jaw) Surgery: This is the definitive treatment to correct the underlying skeletal problem.

• An oral and maxillofacial surgeon performs the operation in a hospital setting under general anesthesia.
• Working from inside the mouth to avoid external facial scars, the surgeon makes precise cuts in the jawbones (a procedure known as an osteotomy). The jaw (or jaws) is then moved into its new, correct, and pre-planned position.
• The repositioned jawbones are secured in place with tiny, biocompatible titanium plates and screws, which are permanent and integrate with the bone as it heals.

3. Post-Surgical Orthodontics: After a healing period of several weeks, the patient will enter the final phase of treatment. This involves several more months in braces as the orthodontist “fine-tunes” the bite, guiding the teeth into their final, perfect occlusion now that the jaw framework is correctly aligned. The entire treatment journey can take two to three years but offers a permanent solution.

I always emphasize that treatment isn’t just about looks, fixing jaw misalignment can improve speech, chewing, and prevent long-term dental damage.

Prognathism is a common condition of jaw misalignment that is most often an inherited trait. While for some it may be a minor part of their unique facial structure, for others it can cause significant functional difficulties with eating and speaking, and aesthetic concerns. It is crucial to understand that a significant jaw misalignment is a skeletal issue, not just a dental one. For those affected, a well-planned and expertly executed treatment journey involving both orthodontics and corrective jaw surgery is a transformative process. Patients often share that correcting prognathism didn’t just change their profile, it changed their confidence, comfort, and how they interact with the world.

American Association of Oral and Maxillofacial Surgeons (AAOMS). (n.d.). Corrective jaw surgery. Retrieved from https://myoms.org/what-we-do/reconstructive-surgery/corrective-jaw-surgery/

American Association of Orthodontists (AAO). (n.d.). Surgical orthodontics. Retrieved from https://aaoinfo.org/blog/surgical-orthodontics/

National Institutes of Health, MedlinePlus. (2023). Prognathism. Retrieved from https://medlineplus.gov/ency/article/003026.htm

Mayo Clinic. (2023). Orthognathic surgery and jaw alignment. https://www.mayoclinic.org