 One of the most common problems orthodontist are asked to treat is the discrepancy that occurs when the upper teeth protrude beyond the lower. Ordinarily when we see a patient with the upper teeth protruding, we tend to think that the upper jaw and teeth are too far forward; but, more often than not, this condition is due to a small lower jaw that is further back than it should be.
With these patients, the orthodontics would like to encourage the lower jaw to catch up in growth, and the Herbst appliances helps make this happen. It is called a "functional" appliance because it causes the patient to function (speak, swallow, and eat) in a new jaw position. If the patient functions in this new position for long enough, the change becomes permanent. The upper jaw and teeth are pulled back and the lower jaw and teeth are pulled forward to create a better bite and a better facial balance and appearance.
Many times the upper jaw must be widened for the lower jaw to be moved forward. This can be done with an expansion screen on the Herbst or with a separate palatal expander appliances used before placing the Herbst.
The Herbst is fixed to the teeth by crowns (caps) that are cemented to the upper first molars and the lower bicuspid teeth. A piston and cylinder attached to the upper and lower segments of the appliance together. These sliding pistons will allow the jaw to open and close, but keep the jaw forward in the desired position.
The Herbst is checked every 8-10 weeks and can be advanced or moved forward more by adding "shims" to the pistons. It stays in place for 8 to 12 months to make sure the correction is permanent and then is removed and full braces are placed to continue and finish the straightening process.
 The Maxillary Palatal Expander is an orthopedic appliance, attached to your upper teeth, that widens the upper jaw. It is used when the upper jaw is too narrow for the lower jaw (cross-bite), or when upper teeth are crowded or blocked out of the arch. The expander can either be attached to the upper molars by cemented bands or bonded, with plastic pads that fit over the upper back teeth. The bonded expander is used more frequently with younger people who still have some baby teeth, while the banded expander is usually used in patients with all permanent teeth.
The upper jaw is made up of two separate bones (right and left halves) connected by a thin band of elastic tissue. While the patient is still growing, this tissue is responsive to stretching forces applied by the expander. As the screw is turned, the wires and bands put an outward pressure on the teeth exerting a force on the bone in the roof of the mouth. This outward pressure stimulates bone formation between the two halves of the upper jaw, increasing the overall width.
Both types of expanders have a screw in the middle, which is turned once a day with a special key we provide. As the jaw gets wider, it is normal for a "gap" to develop between the upper front teeth. This space will eventually close on its own after the expansion has been stopped, or it can be closed with a few brackets.
It is important to turn the screw the prescribed number of turns. If you forget to turn one day, you can make it up the next day, but do not exceed the total number of turns. We do not want you to go too far. We will evaluate your progress at your next appointment and determine if further expansion is necessary.
 The Transpalatal Arch is a wire that goes across (trans) the roof of the mouth (palate). It is soldered onto bands that are then cemented onto the two upper first molars.
The TPA is most often used when bicuspids have been extracted to passively hold the molars from drifting into the extraction spaces. The heavy wire between the bands ties the molars together preventing any unwanted movement.
The TPA can also be used as an "active" appliance to move teeth orthodontically. By placing bends in the wire before inserting the appliance, the molars can be widened, moved backward, or rotated. The loop at the top of the TPA can even be used to teach proper tongue position in patients with a poor tongue posture.
 The Lower Space Maintainer consists of a wire that runs behind the front teeth, and connects to a band on either side. It does just what the name implies, it "maintains space" in the lower jaw for teeth that are going to erupt later.
The lower "baby" second molars are nearly 2-3 millimeters larger than the adult premolars that replace them. By holding the space after these baby molars fall out, we can use the space to our advantage to help resolve crowding problems later. Without a space maintainer in place, the permanent first molars drift forward and this valuable space is lost. A space maintainer is frequently used to preserve space when baby teeth are lost prematurely due to decay.
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