What is prognathism?

Prognathism refers to a bony abnormality of the face that causes a marked protrusion of either the upper or lower jaw.

Maxillary prognathism, also known as an overbite, is more common and not always as noticeable as Mandibular prognathism, more commonly known as an underbite.

This condition frequently causes the teeth of the lower jaw to cover the upper teeth in a way that adversely affects breathing, appearance, speaking, biting and chewing.

Both Protruding lower jaw and small lower jaw (micrognathia) can have an impact on aesthetics Both these problems could be addressed surgically if the lower jaw is set in place.

What are the causes of prognathism?

Prognathism affects individuals of all ages and has been shown to be caused by a variety of factors. These include:

• Hereditary factors, such as a family history of protruding or abnormal jaws
• A medical condition or genetic disorder, such as Crouzon Syndrome or Down Syndrome
• Gigantism – Overgrowth of the body tissues due to overproduction of growth hormone
• Basal cell nevus syndrome – It is a rare inherited condition leading to abnormal facial features like lower jaw protrusion.
• Growth hormone disorders that cause excessive growth of the jaw
• Achondrogenesis – It is an inherited disorder where sufficient growth hormone is not produced by the pituitary gland.

What are the types of surgeries?

In most cases of prognathism, a combination of jaw surgery and orthodontic treatment is used to correct the malocclusion, or misalignment, of the jaws. Depending on the type and severity of the condition, the procedure may involve surgical modification to one or both of the jaws.

Cutting the bone is called osteotomy and in case of performing the surgery on the two jaws at the same time it is called a bi-maxillary osteotomy (two jaws bone cutting) or a maxillomandibular advancement.

The types of surgeries that are performed for lower jaw and small lower jaw correction are:

Le fort osteotomy

The LeFort I osteotomy is one of the most commonly used procedures to correct midface deformities. It allows for correction in three dimensions including advancement, retrusion, elongation, and shortening. It is indicated, often in conjunction with mandibular surgery, for class II and III malocclusion, facial asymmetry, obstructive sleep apnea, and maxillary atrophy.

Mandible Osteotomy:

It is intended for those with a receded mandible or an open jaw, which may cause difficulty in chewing and jaw pain.

Sagittal Split Osteotomy:

It is used to correct the mandible retrusion and prognathism. This procedure is used to change the position of your lower jaw so that your teeth can be aligned. It is an intraoral surgical procedure for correction of retrognathism and prognathism.

Bilateral Sagittal Split Osteotomy

In this procedure, the lower jaw is split bilaterally to straighten it to a balanced and functional position. This surgery is useful to correct the types of malocclusion, a misalignment of teeth and jaws.

Inter maxillary fixation

The jaws will be wired together (inter-maxillary fixation) using stainless steel wires during the surgery to ensure the correct re-positioning of the bones. This in most cases is released before the patient wakes up

Which individuals are eligible for the surgery?

The surgery is indicated for the individuals with:

• Misaligned jaws
• Bite problems
• Chronic jaw or jaw joint pain
• Excessive wear of the teeth
• Unbalanced facial appearance
• Open bite (a space is formed between the upper and lower teeth when the mouth is closed)
• Facial injury or birth defects
• Protruding jaw
• Receding chin
• Inability to make the lips close without straining
• Chronic mouth breathing and dry mouth

How should I prepare for the surgery?

Before the surgery, your surgeon may advice you to follow certain instructions:

• Avoid smoking and alcohol intake
• Sleep well the day before surgery
• Stop eating or drinking for six hours before your surgery
• Notify your surgeon if you have any illness like cold, cold sore, stomach or bowel upset

What will happen during the surgery?

General anesthesia is given before the procedure and the wisdom teeth are extracted to make space for mandibular movements posteriorly if required.

The surgical procedures of the mandible osteotomy and sagittal split osteotomy are explained below:

Mandible osteotomy

The operation is undertaken through an incision made at the back of the mouth in the gum by the molar teeth to gain access to the jaw. The lower jaw is then cut in an oblique fashion with a small saw to allow it to be broken in a controlled manner. It is then moved into its new position, which has been predetermined during surgical planning with the aid of models of your teeth. A small plastic wafer is attached to the teeth to allow the new position of the lower jaw to be determined, which is then fixed into place with small metal plates and screws.

Sagittal split osteotomy

A horizontal incision is made at the ramus mandibule and extended to the anterior portion of ascending ramus. A second incision is made inferiorly on the ascending ramus to the descending ramus. This cut is extended to the lateral border of mandible between the first and second molar. A vertical is also made extending to the inferior area of the mandible. All these incisions are led to the middle area of the bone and a chisel is inserted into these cuts. The chisels tapped gently to split the mandible. Now, the mandible is adjusted into the new or the predetermined position and stabilized using stabilization screws. After adjusting the mandible to the position, the jaw is wired for approximately 4 to 5 weeks.

What is the aftercare of the surgery?

After orthognathic surgery, patients are often required to adhere to an all-liquid diet. After time, soft food can be introduced, and then hard food. Diet is very important after the surgery, to accelerate the healing process. Weight loss due to lack of appetite and the liquid diet is common,You may have to refrain from tobacco usage. You must avoid strenuous physical activities. Pain and swelling after the surgery last for about few weeks. Pain medication helps to keep the pain in control. Normal recovery time can range from a few weeks for minor surgery, to up to a year for more complicated surgery.

What are the post-surgical recommendations?

Approximately 3 to 6 weeks after surgery, you should return to your surgeon to begin post-surgical treatment (to improve the stability).

After the surgery, you will have improved aesthetics.

• You may have post surgical depression. You will feel better with the improvement in the aesthetics and as the time passes after the surgery.
• Pain and swelling are common. The pain is controlled by medications and will depend on the individual’s psychological state. Swelling reaches the peak after about 36-48 hours of the surgery. It decreases slowly and is completely gone after about 6 weeks of the surgery.
• If your jaw stabilization is by use of light elastic bands, chewing and swallowing is not a problem, you will be able to do these activities immediately after a day of the surgery. But, if the lower jaw is attached to the upper by a wire, then you may have a problem with swallowing, eating, chewing, and speaking. You may find it a bit difficult, but slowly you will be able to perform all these activities.
• You can have a loss of sensation in the lips after the surgery. This occurs due to the injury to the nerve. You will regain the sensation gradually, but it can take few months. For some, the sensation may be lost forever.
• You will not have any scars on the face as the surgery is performed from inside the mouth. These scars fade away with time. Sometimes, ointments are prescribed to remove the scars.

During an evaluative consultation, the plastic and reconstructive surgeon and orthodontist will assess the patient’s type of prognathism and level of protrusion. Any symptoms related to the condition, such as difficulty breathing, talking or eating, will be noted. In addition, the patient will be asked to identify any other symptoms that may be associated with the prognathism, as a protruding jaw may indicate other, more complicated medical issues. Family history may be discussed as well in order to determine why and approximately when the condition developed, as well as how the jaw is expected to change in the future.

In addition to the initial assessment, the surgeon may order a variety of diagnostic tests in order to more accurately determine the severity of the condition. One or more of these tests may be necessary:

• CT scan of the face
• Lateral cephalogram
• Panoramic dental x-rays
• Bite imprints to allow for the construction of a mold