Expanders

What is an expander?

A common appliance in orthodontics is the use of a palatal expander. An expander is used to actually widen/separate the bones of the upper jaws. This is analogous to moving the foundation of a house and the house moves with the foundation. In this case, as the bones are moved, the teeth move with them.

What are the indications for expansion?

The usual reason for expansion is correction of crossbites, correction of crowding, and correction of axial inclination of maxillary posterior teeth. The upper teeth should normally fit over the lower teeth, like the lid on a box.

How do the bones expand?

Most people think bones are like cement, or like a rock. That is not the case. The sutures down the middle of the palate are actually two individual bone plates which become more and more inter-digitated with age. By age 14 or older the suture becomes so inter-digitated that it is effectively “fused”. As the bones separate during expansion, it creates a vacuum or void between the bone plates. Your body will grow new bone in that void and that will become your new skeletal position.

What is the best age for expansion?

During expansion ideally you want skeletal expansion (move the bones) as opposed to dental expansion (move the teeth). As the bone sutures become more inter-digitated (fused), true skeletal expansion becomes more difficult. Therefore, younger patients benefit most from expansion as their bones are more pliable and malleable. Generally, by the time a patient has reached 14 years of age the only expansion that is taking place is unstable dental expansion.

Can expansion eliminate the need for extractions?

One of the indications for expansion is to create enough space so that it minimizes the need for extractions. For every 1mm of increased width (across) there is an increase of 0.7mm in arch perimeter (around). Expansion can minimize the need for extractions, but you cannot expand your way out of all crowding problems.

Is there a limit to how far we can expand?

There are anatomic limitations to how much expansion can take place, and there are physiologic limitations to expansion as well. There exists a balance between cheek pressure and tongue pressure where tooth position is stable. If this balance is artificially over-expanded it will collapse once the expander is removed until balance is restored.

Can the lower arch be expanded?

There are no sutures to be expanded in the lower arch, therefore any lower arch expansion is purely dental tipping. Our office does not use lower arch expanders as this dental expansion is highly unstable. This position is shared by the American Board of Orthodontists which penalize cases that expand inter-canine width on the lower arch.

Will it hurt?

During the active expansion, you will feel pressure in the cheek bones and tingling in the nose. This pressure will be greatest each time the expander is activated (usually twice a day). Once the expansion is complete there will be no additional discomfort.

How long will the expansion take?

Usually active expansion occurs in 2-3 weeks, and is stabilized for 3-6 months to allow new bone fill. Sometimes we will use retainers for stabilization. Other times we will keep the expander cemented in the mouth to act as the retainer.

It looks like you over-expanded!

It is well established in studies that there will be 30% relapse of any palatal expansion. We therefore will overshoot our target so that when relapse occurs we still have our desired expansion.

How do I keep it clean?

Keeping expanders clean is a constant challenge. They tend to accumulate plaque and food quite easily. Diligent home care is crucial to prevent decay while wearing an expander. We will give you all the tools and cleaning aids you need to keep your expander clean.