Jaw reduction is a type of surgery in which the objective of treatment is to narrow the lower one-third of the face—particularly the contribution from the mandible and its muscular attachments. There are several techniques for treatment—including surgical and non surgical methods.

Facial aesthetics

A square lower jaw is generally considered a very masculine trait. Widening of the lower third of the face can cause either a square appearance to the face as a whole or can distort the natural appearance of the angle between the chin and the neck.

Whereas square lower jaws are often considered a positive trait in men, a wide mandible can cause significant facial discordance and/or masculinization of the female face. Even in certain men, the size of the lower jaw can cause facial disharmony—particularly when there is asymmetry.

A wide lower face can primarily be caused by enlargement of the mandible or masseter muscle

Masseter muscle

In human anatomy, the masseter is one of the muscles of mastication.In the animal kingdom, it is particularly powerful in herbivores to facilitate chewing of plant matter.-Origin and insertion of the two heads:...

.

Causes

The primary cause of an enlarged mandible is developmental or congenital. There are some rare disorders that can further widen the jaw such as acromegaly

Acromegaly

Acromegaly is a syndrome that results when the anterior pituitary gland produces excess growth hormone after epiphyseal plate closure at puberty...

.

Conversely, while a masseter muscle can be large due to congenital reasons, it can commonly be an acquired deformity. Like any muscle it increases in size with exercise. Behaviors such as repeated gum chewing, teeth clenching, or bruxism

Bruxism

Bruxism is characterized by the grinding of the teeth and typically includes the clenching of the jaw. It is an oral parafunctional activity that occurs in most humans at some time in their lives. In most people, bruxism is mild enough not to be a health problem...

 can contribute to enlargement of the muscle.

Techniques

There are several jaw reduction techniques available—both surgical and non-surgical. Ideally prior to selection of a treatment, the patient is examined to determine whether the cause is due to the bone

Bone

Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

, the masseter or both. Additionally, if a treatable cause is present it should be identified.

Botox injection

Non-surgical techniques are essentially limited to cases in which the masseter is enlarged. A convenient method to treat an enlarged muscle is through the use of botox

Botulinum toxin

Botulinum toxin is a protein produced by the bacterium Clostridium botulinum, and is considered the most powerful neurotoxin ever discovered. Botulinum toxin causes Botulism poisoning, a serious and life-threatening illness in humans and animals...

 injections. Botox is injected into the enlarged muscle, weakening it so it slowly becomes smaller through atrophy

Muscle atrophy

Muscle atrophy, or disuse atrophy, is defined as a decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle. When a muscle atrophies, this leads to muscle weakness, since the ability to exert force is related to mass...

 over several months. There is no down-time and improvement is gradual—individuals who interact with the patient may never know that a plastic surgical procedure was performed

The use of Botox for jaw reduction has been studied scientifically. Improvement is generally not seen for at least 2 - 3 weeks. Peak improvement occurs at months 3 to 9 with good results still observable at one year in many patients.

The procedure can result in temporary paralysis

Paralysis

Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...

 of the muscles that move the lips, a rare but acknowledged complication.

Surgical reduction

Surgical techniques are used to directly reduce the size of an enlarged mandible. Incision can be to the inside or outside of the mouth, though the internal incision is the most common because it leaves no visible scar. A burr is used to remove the outer layer of the enlarged mandible, narrowing the jaw.

Potential complications include injury to the inferior alveolar nerve

Inferior alveolar nerve

The inferior alveolar nerve is a branch of the mandibular nerve, which is itself the third branch of the trigeminal nerve .-Path:...

which provides sensation to the lower lips and teeth.