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The Herbst Appliance

Correcting Orthodontic Problems Caused by Uneven Jaw Development

A Consultation with Dr. Peter Ngan

Dear Doctor,
My orthodontist says my daughter needs to wear a Herbst appliance to correct problems with her bite. Can you tell me more about what this device is and how it works?

Dear Carla,
Most everyone has seen common orthodontic appliances like braces, retainers and rubber bands (elastics). But many people aren't familiar with devices like the Herbst appliance, which we call "functional appliances." These devices are designed to transmit steady, gentle forces that can influence the growth and development of the teeth and jaws. This in turn can help children develop a better bite and even an improved facial profile.

Herbst appliance.
The Herbst appliance uses steady, gentle forces to promote the forward growth of the lower jaw while slowing down the development of the upper jaw.

Traditional braces are great for correcting a crooked smile, or changing the position of teeth to improve the way they fit together. But some youngsters have bite problems that are caused by a discrepancy in growth between the upper and lower jaws. When the upper jaw develops more than the lower jaw, it can cause the top teeth to protrude (stick out) far in front of the bottom ones. This may lead to kids being teased about their appearance; it can also make their upper front teeth much more prone to traumatic injuries because they aren't protected by the lips.

In this situation, the Herbst appliance can really help. It works like elastic bands to move the upper teeth back, with one important difference: The person who wears it doesn't have to put it in each day. The top part of the device consists of two small metal tubes, hinged to bands that are cemented to the upper molars (back teeth) on the left and right sides. On the bottom, two small rods are also hinged to bands that are cemented to lower teeth. The lower rods slide inside the upper tubes—something like a tiny shock absorber—and as they do, they exert a force that gently pushes the lower jaw in a forward direction.

To get an idea of what this does, try positioning your lower teeth ahead of your upper front teeth. You'll feel a pressure pushing the upper front teeth back and the lower ones forward. The Herbst appliance helps supply the force to maintain this jaw posture. The appliance can slow down the development of the upper jaw, which has a natural tendency to grow forward and down. It can also stimulate the growth of the lower jaw, if the child's jaw has growth potential—but not everyone has the genetic capability for this kind of jaw growth. In the latter case, the appliance will simply move the upper teeth back and lower bottom teeth forward.

When a child's upper jaw is ahead of the lower jaw in terms of growth, treatment with the Herbst appliance can help normalize the front-to-back positions of the jaws and improve the facial profile. Typically, this is most effective when a child is growing at the speediest pace—a time we call the pubertal growth spurt, which generally occurs between the ages of 11 and 14 years. However, the Herbst appliance is sometimes recommended for kids as young as 8 or 9, when there's a need to re-position front teeth that may stick out beyond the child's lips. In this case, correcting those protruding teeth with early treatment is an example of interceptive orthodontics.

While the Herbst appliance has become increasingly popular in recent years, it's not the only way to correct orthodontic problems that stem from mismatched jaw growth. The traditional method has been to use elastics and/or orthodontic headgear in combination with braces. A number of retainer-like appliances can be used as well. However, there's a drawback to removable devices like these: They rely on major cooperation from youngsters and their families.

Typically, elastics and retainer-like appliances need to be worn a minimum of 22 hours a day to be effective; headgear, which may include neck or chin straps and thick wires extending outside the mouth, must be worn for at least 12 hours daily. But today, both children and adults face numerous demands on their time. Sports, jobs and other responsibilities make it more difficult to keep regular schedules—and unfortunately, kids don't wear the devices as much as they should. But unlike removable appliances, the Herbst appliance is fixed: It stays in the mouth all the time, and can't be taken off at home. That means it works 24 hours a day, and compliance isn't an issue.

However, there are a few things that children who wear the Herbst appliance will need to get used to. Since the upper and lower jaws are being held in a different position, it may take a few days before swallowing feels natural. Eating may also be a challenge at first, in part because the teeth may actually be closing together for the first time. I usually suggest that kids try a softer diet, like macaroni and cheese or a vegetable stew, for two or three days. Finally, most kids will have to adjust to speaking normally with the appliance. I recommend they practice reading aloud to themselves for a few hours; parents may also want to let teachers know about their children's treatment to avoid surprises.

Parents and kids should also be aware that keeping up good oral hygiene takes a bit more attention while wearing the appliance. I generally do a lot of teeth cleaning when young patients come in to my office. In between visits, I recommend that kids use an over-the-counter fluoride rinse after brushing at night; this can help strengthen tooth enamel and prevent cavities. Using a water flossing device (water pick) after meals may also help clear food debris from hard-to-clean spaces.

I hope this brief explanation helps you understand why the Herbst appliance might be recommended for kids who have dental problems related to mismatched jaw growth. If you have more questions, I'm sure your orthodontist would be glad to address them.