Jaw deformity

What is jaw deformity?

A jaw deformity is when your upper jaw, lower jaw, or both, haven't grown or developed to fit together properly, so your teeth don't meet as they should and the shape of your face may be affected. It can range from a mild difference in bite to a more noticeable change in facial appearance, and it's usually possible to correct surgically.

Symptoms of jaw deformity

Jaw deformities can cause a range of practical problems. You might have difficulty speaking, chewing, swallowing or breathing, and the strain can also affect your jaw joint (the TMJ) and facial muscles, which over time may harm your gum and tooth health. Pain, clicking and wear in the jaw joint are also common.

You may also notice changes to how your face looks, such as:

• an overbite or underbite, where your teeth don't line up properly
• a ‘gummy smile’, which happens when your upper jaw sits lower than it should, showing more gum than usual when you smile
• a long, open-looking face with a gap between your top and bottom teeth even when your jaw is shut
• a jaw that looks too small, sometimes hiding your teeth almost completely
• one side of your face looking noticeably different in size or shape from the other.

Beyond the physical symptoms, many people find the effect on their appearance affects their confidence, particularly younger people who tend to be more conscious of how their face looks.

Causes and risk factors

In most cases, a jaw deformity develops because the upper and lower jaw grow at different rates, or one grows too much or too little. Genetics can play a part, so it may run in your family, and some birth conditions, such as cleft lip and palate, are also linked to jaw deformities.

Injury is another common cause, particularly injury to the jaw joint itself, whether from a childhood accident or a difficult birth such as a forceps delivery. Repeated middle-ear infections have also been linked to this kind of joint damage, which can disrupt the growth centre in the jaw joint and change how the jaw develops from that point onwards.

Sometimes the joint itself fuses solid, a condition called TMJ ankylosis, which can follow an injury, an infection or a previous operation that hasn't healed as expected. In children and teenagers, juvenile idiopathic arthritis, a form of childhood arthritis, can also damage the jaw joint and lead to a jaw deformity that gets gradually worse as the child grows.

Because the jaw joint keeps developing throughout childhood, children and teenagers are more vulnerable to this kind of growth disturbance than adults.

Types of jaw deformity

Jaw deformities can take several different forms, and you may have more than one at once. Your jaw might be too big or too small for the rest of your face (sometimes called hyperplasia or hypoplasia), or it might sit too far forward or too far back (known as prognathism and retrognathism).

Other deformities affect symmetry, where one side of your jaw or face has grown differently to the other, or how your teeth meet, causing an overbite, underbite, open bite or crossbite.

How is jaw deformity diagnosed?

Diagnosis usually starts with your surgeon or dentist asking about your medical history and carrying out a full physical and dental examination. This will look at the proportions of your face, how well your jaw and teeth function, your dental hygiene, including whether your gums have receded, and whether your airway is affected, since some jaw deformities can contribute to sleep apnoea.

X-rays and other imaging scans of your face are usually taken too, to help your surgical team plan the best treatment approach. If a problem with your jaw joint's movement is suspected, they'll also assess how far you're able to open your mouth.

How is jaw deformity treated?

Non-surgical treatment

Some milder problems with how your teeth meet can be managed with orthodontic treatment, such as braces or other appliances, to bring your teeth into a better position.

For a true jaw deformity, though, orthodontics is usually used to prepare your teeth before surgery, or to fine-tune your bite afterwards, rather than as a treatment on its own.

Surgical treatment

The main treatment for jaw deformity is orthognathic surgery, where your surgeon surgically resets your jawbone, or both jawbones, so your bite and profile line up as they should. Your surgeon can build up, trim down or reshape the bone as the surgery needs, and because the soft tissue around it, your chin, cheeks, lips and nose tip, shifts along with the bone, this kind of surgery often improves the balance of your whole face, not only your bite.

Because surgeons usually work through the inside of your mouth, you're unlikely to be left with scars anyone else can see. To keep everything stable while it heals, your surgeon might fasten your jaws together with wires or elastic bands on your teeth, or fix things internally with small plates and screws; the second option often lets you start moving your jaw again sooner.

Bigger operations often mean a short stay in hospital, whereas more minor procedures can sometimes be done with you going home the same day.

If TMJ ankylosis (a fused jaw joint) is the underlying problem, your surgeon will need to free up the joint first, typically by cutting away the fused bone to open a gap, then packing that space with soft tissue, often a piece of muscle, so the bone doesn't grow back together.

The resulting jaw deformity is then corrected with orthognathic surgery or with distraction osteogenesis, a technique where a small device slowly pulls the cut bone apart, encouraging fresh bone to grow and fill the space naturally. This means you avoid a separate operation to take a bone graft from elsewhere in your body, and the results tend to hold up well over time.

In more severe cases, such as significant jaw joint damage from juvenile idiopathic arthritis, the jaw joint itself may need to be rebuilt or replaced at the same time as the jaw is repositioned.

Where possible, surgeons prefer to wait until jaw growth is mostly finished, usually from around 15 in girls and 17 to 18 in boys, to reduce the chance of needing further surgery later, although earlier surgery may be necessary for severe pain, breathing difficulties or problems with eating.

When should I see a doctor?

If you're having ongoing problems with speaking, chewing, swallowing or breathing, notice pain or clicking in your jaw joint, or you're unhappy with how your bite or facial profile looks, it's worth getting this checked by a dentist or doctor. They can assess whether a jaw deformity is the cause and refer you to an oral and maxillofacial surgeon if needed.