Functional Orthodontic Appliances

The standard orthodontic treatment plan consists of a period in braces followed by the use of a retainer. However, some patients will require additional intervention to achieve healthy alignment. In cases where jaw misalignment exists, the orthodontist may add a functional appliance to the course of treatment–either before or concurrent with braces. This type of appliance is designed to reshape the jaw, correcting problems with the bite and allowing room for the teeth to fit into their correct positions.

In most cases, treatment with a functional appliance will last up to one year. Functional appliances are worn almost exclusively by younger patients who have jaws that are still developing. Adult patients with severe jaw irregularities often require surgery, as their bones have finished growing and can no longer be directed into the correct positions.

Your orthodontist has many options for jaw correction using functional appliances, and the type selected will depend on the specific problem with the shape and position of the jaw bone.

Space Maintainer

When children lose primary teeth earlier than expected or permanent teeth are late to grow in, a space maintainer might be needed to hold the positions for the permanent teeth before orthodontic treatment. When a tooth is missing for too long, other teeth can loosen and move into the empty position, which can guide permanent teeth into incorrect positions. A space maintainer will hold the positions so that new teeth grow correctly.

There are two main types of space maintainers:

  1. Removable – removable space maintainers are similar to the orthodontic retainers worn after braces, and they are usually made of metal or acrylic. In some cases, an artificial tooth may be attached to the space maintainer and used to fill a gap that must remain open for the unerupted tooth.
  2. Fixed – there are four different kinds of fixed space maintainers: unilateral, crown and loop, distal shoe and lingual.
    • Unilateral spacers wrap around the outside of the tooth and connect to a metal loop that holds the space intact.
    • Crown and loop spacers are placed on one side of the mouth to hold space open for one tooth. The crown covers the tooth and attaches to the loop to ensure enough space for the erupting tooth.
    • Distal shoe spacers are usually used for an unerupted first permanent molar. They are more complicated space maintainers because the end of the metal is usually inserted into the gum line to keep the space from closing. Your orthodontist will need to monitor the progress of the permanent molar as it gradually shifts into its intended space.
    • Lingual spacers are usually placed on both sides of the mouth and can be cemented to molar teeth and connected by a wire on the inside of the lower front teeth. Usually, these spacers are used for more than one missing tooth.

Palatal Expander

A palatal expander is used to stretch and widen the arch of the upper jaw, providing enough space for the teeth to realign. The upper jaw develops in two halves that don’t fuse until the teenage years, so in children, the bones can be gradually separated and stabilized. Palatal expanders also can correct crossbites, a malocclusion where the upper teeth sit inside the lower teeth.

This type of expander is custom-made for each individual and fits over several top teeth in the back of the mouth. It can be worn with or without concurrent treatment with braces.

  • A rapid palatal expander has a screw that connects the two halves of the appliance in the middle. The patient activates the expander by turning a key in part of the appliance as instructed by the orthodontist. This creates tension at the junction of the two palatal bones, causing them to gradually move apart until the lower teeth no longer close against the outside of the uppers.
  • A quad helix is a fixed expander for the upper jaw that does not require a key to activate. It can be used to widen the upper jaw in the front and/or the back, as well as to rotate the upper first molars. A quad helix expander also can be used to widen the upper arch to make room for crowded teeth or to correct a dental crossbite.
  • A removable palatal expander might be appropriate if the jaw needs only a small amount of widening. However, even though the term removable suggests that it can be taken out, the patient needs to wear it nearly 24 hours per day, with the only exceptions being during meals and while cleaning the teeth.

Bionator & Twin Block

If your child’s jaws are not growing in proportion to one another, the orthodontist may recommend a bionator device. The bionator positions the lower jaw forward, helping the teeth to erupt and align properly. This dental appliance is successful in reducing extensive orthodontic treatments later on, and it helps to promote natural-looking alignment. There is no pain or discomfort when wearing it, and it should be removed only when eating, brushing, flossing or playing contact sports.

A twin block is similar to a bionator but has separate upper and lower components that interlock and posture the lower jaw forward. Like the bionator and other removable fixed appliances, twin blocks are meant to be worn almost both day and night. It is activated each time the patient bites, chews, swallows or talks by exerting gentle pressure on the teeth and dental arches while stabilizing the jaw joints.


Headgear can correct growth differences between the upper and lower jaws that cause the front teeth to protrude (often called “an overjet” or “buck teeth”). It also can be used to reserve space for new teeth or correct an overbite. The headgear is removable, so it is important to make sure it is worn at least 14 hours per day. For most patients, this means after school each day and through the night.

Orthodontists prescribe headgear when they need more force to move the teeth compared to braces alone. The headgear attaches to metal hooks or a facebow and straps around the back of the head or neck. The teeth will probably feel somewhat sensitive and sore after each adjustment, but similar to regular adjustments with braces, the pain will subside within a couple of days. Headgear is one of the most effective appliances available to correct Class II malocclusions.

Herbst & Forsus Appliances

A Herbst appliance is very effective in correcting large overbites by enhancing the growth of the lower jaw in a forward direction while applying pressure to the upper jaw in a backward direction. It is a metal tube and rod that is attached to the top molars and bottom teeth. It is still possible to move the mouth from side to side, but the device prevents the jaw from moving toward a protruded position.

The Forsus appliance is similar to a Herbst in that it also is used to treat overbites and is a fixed appliance that attaches similarly to the upper and lower teeth, but a Forsus has spring coil rods instead of solid ones. It often is used in place of elastics or headgear, so the patient does not need to worry about remembering to wear it. It typically is placed about six months into the orthodontic treatment period.

Regardless of the type, functional orthodontic appliances are used to treat irregular bites and malocclusions in children and young adults while the jaws of the bones are still forming. If you think your child might need orthodontic treatment to get the smile they deserve, contact us today to schedule your complimentary consult with one of our board-certified orthodontists.


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