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 Caucasian and many Asian men, a wide mandible can cause significant facial discordance and/or masculinization of the female face-particularly in those of East Asian descent. 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.
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.
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 can contribute to enlargement of the muscle.
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, the masseter or both. Additionally, if a treatable cause is present it should be identified.
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 bur is used to remove the outer layer of the enlarged mandible, narrowing the jaw
Potential complications include injury to the inferior alveolar nerve which provides sensation to the lower lips and teeth.