How Do Palate Expanders Work? All Your Questions Answered

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Hey there, if you’re a parent researching the palate expanders your child is about to wear, I’ve got you covered. And if you’re a patient, welcome! I know palate expanders are intimidating, but they’re actually great, and there’s nothing to worry about.

I’ve placed hundreds of palate expanders over the years, and if used properly, they do a spectacular job of truly widening the upper jaw and creating the space we need. But how do they work, exactly, and how do they “widen” bone? That’s what I want to cover in this article.

Palate expander components & Their Purpose

There are several types of palate expanders, but I’m going to cover the most popular types of fixed expanders. You can check the variations in the gallery below (images courtesy of Universal Orthodontic Lab):

It’s obvious from the images above that what most palate expanders have in common is: bands on the first molars and a strong screw that sits on top of the palate. Everything is connected through thick metal wires (or arms) that can withstand the high forces created by the screw.

The only exception to this setup is the bonded palate expander. You’ll see thick acrylic pads on both sides that cover multiple teeth. The bonded palate expander is used in certain situations where banding the first molars isn’t possible, or when we want to correct certain types of bites.

The types of expanders used by orthodontists in order of popularity are these:

  • Classic Palate Expander
  • Compact Palate Expander (the screw is smaller and doesn’t require as much wire)
  • Bonded Palate Expander (uses acrylic pads on multiple teeth instead of molar bands)
  • Fan Type Palate Expander (the screw opens in a V shape for maximum frontal expansion)
  • Haas Palate Expander (uses acrylic padding on the palate to achieve better lateral expansion)
  • MARPE Palate Expander (uses bone miniscrews to achieve expansion in adults and teenagers)

Now that you’re a little more familiar with all the shapes and sizes of a palate expander, know that if your kid is 13 and under, he or she will probably receive a classic or bonded palate expander. You can read this article to understand more about the optimal age to get an expander, and the difference between banded and bonded.

If you’re an adult getting braces, or if your child is older than 14, your orthodontist may suggest getting a MARPE expander. Since expansion is nearly impossible with normal expanders after a certain age, the MARPE method does an almost surgical job of opening the suture, sans the surgery. You can read all about it in this article.

Lastly, the most important aspect of a palate expander is that it is cemented, so you can’t take it off whenever you like, and it has a screw that needs to be activated by the patient, every single day, for a set amount of days.

We’ll cover why it’s so important that your palate expander stays on, and how exactly to use the screw in the following sections.

How does it all work?

Did you know that palate expansion was discovered accidentally? It goes as back as 1860 when a dentist named Angell placed a screw between the premolars of a 14-year old girl. When she returned, 2 weeks later, he noticed a gap between her front teeth.

At the time, Angell’s discovery was rejected by rhinologists and dentists alike, and the idea of maxillary expansion was only revisited decades later. Now, over a century from the first standardized expansion, we can confidently say that palate expanders have become a routine part of any orthodontic practice.

So how does it all work?

The maxilla is the bone that makes up the upper jaw and is composed of two halves, each of which forms the roof of the mouth and the floor of the orbits (eye sockets). The two halves of the maxilla are joined together in the center by a suture, which is a fibrous joint that allows for some movement between the bones.

During rapid maxillary expansion, the orthodontic appliance exerts a gradual and continuous outward force on the two halves of the maxilla, causing the suture to stretch and open. This process triggers a biological response in the body that causes the bone to remodel and create new bone tissue, filling in the gap created by the expanding suture.

As the maxilla widens, the dental arch also expands, creating more space for the teeth to move into their correct positions. The expansion can also improve breathing and help correct other orthodontic issues, such as crowding and crossbite.

Turning the screw

Palatal expanders are also called RPEs, which stands for Rapid Palatal Expanders. This is because expansion is done very quickly. It’s the only way to ensure that the suture actually opens, instead of just teeth shifting through bone. The maxillary suture needs a lot of force and constant tension over the course of a few short days to open.

Expect to turn the screw one to two turns per day for a few weeks. Your orthodontist will ensure you understand how the screw works and how many turns to make per day and in total. Don’t worry, during this active expansion phase, you’ll be seeing your doctor more often so that everything goes according to plan.

Here is how you activate the screw, in a nutshell:

  • You’ll receive a key from your orthodontist. Insert the key into the hole of the expander all the way to the notch. If you don’t insert the key all the way, it can slip out.
  • Push the key toward the back of the mouth and turn the screw until you see a new hole. It’s okay to feel some resistance. You need to see the entire hole before attempting to remove the key. This counts as one turn.
  • Some expanders have arrows on them indicating the direction in which to push the key, but it’s easy: the only way you can comfortably turn it is from front to back.
  • When removing the key, do it carefully, without unwinding the screw! Many people don’t pay attention when pulling the key out, and they undo their screw activation.

Aside from unintentionally reversing their screw, the most common mistake patients make is only turning the screw halfway. This doesn’t allow for the next hole to show, or it shows incompletely and you can’t access it.

To fix this mistake, do your best to fit the key into the previous hole and turn it all the way to the back until the next one shows.

YouTube video

The maximum amount of activation on an expander screw is 40 turns, but few patients will actually need 40 turns. Most people need a little less than that. So, depending on whether you’re turning your screw once or twice per day, your expansion phase can take anywhere from 2 to 4 weeks.

If you’re still having trouble turning the key, or getting it inside the hole, save this article for future reference, where we talk all about expander activations.

Rest Period

Once the activation phase is over, your orthodontist will instruct you to stop turning the screw. Some orthodontists prefer blocking the screw with flowable composite so that it doesn’t unwind from all the forces it’s subjected to.

All you have to do now is take great care of your appliance, and wait. Treatment with palatal expanders may take 4-6 months, but only one of those months is actual active treatment. The rest of the time, we just want to check that everything is still in place, so you’ll still be seeing your orthodontist every 4-6 weeks.

The most important thing you have to do as a patient during these 4-6 months is to make sure you’re eating the right foods and avoid your expander getting loose, which can undo all the progress. We have articles on both eating with a palatal expander and how to know when it’s loose.

Now that your maxilla is widened and the suture is open, there’s really nothing holding the maxilla halves apart except for the expander itself. If you look at an X-ray of the suture, it feels like there’s nothing but thin air in between the two plates. But don’t worry, our body is smart and it will create new bone to fill in the gap in a matter of months.

All about that gap

The greatest indicator of true maxillary expansion is a large gap that appears between the central incisors. Most patients and parents are amazed to see these changes in such a short time, and since they’ve been warned in advance, they don’t get too worried.

Every turn of the screw will, at least in theory, produce .25 mm of expansion. This means that we could potentially achieve 10mm of space on the arch if we turn the maximum number of turns on our screw. We rarely do that, and 7-8mm of expansion is a more realistic goal to shoot for.

All that extra space isn’t equally distributed between your teeth and it will manifest as a large gap between the front teeth. This is because, when the two maxilla halves separate, they often separate more in the front and less in the back, in a slight V shape.

We’ll later use that gap to redistribute the space throughout the arch. If you have dental crowding, it can start to naturally correct by itself, with a little help from the gum fibers that stretch and want to bring your front teeth together.

However, if you don’t have crowding, but need to correct something like a crossbite, it will take a little longer to close that gap.

Fixed vs. Removable palate expanders

You may have researched palate expanders and discovered that there was also such a thing as removable palate expanders. So why not go for that option?

While removable clear aligners that you take off whenever you want work (almost) just as well as fixed braces, we can’t say the same thing about removable palate expanders.

There’s a huge difference between the two: with fixed expanders, we’re actually widening the maxilla by opening the suture and creating more bone. With removable expanders, you only turn the screw once or twice per week, so all you do is push teeth around.

Yes, your kid’s arch will be wider with removable palate expanders, and their teeth will appear straighter, but there’s a lot of tipping involved, and the effect on the suture is insignificant. Plus, with removable expanders, there’s a big compliance factor, and most kids fail to wear them enough.

Will the palate expander change your face?

YES. Palate expanders, if used efficiently, will widen the maxilla, but we’re talking millimeters here. Studies have demonstrated changes in both the transverse and vertical plane. If your child previously had a narrow face, you’ll see more obvious changes, and even a change in their jawline as a consequence of braces and elastics.

The changes are more obvious in younger children, and almost insignificant in older patients. Growth takes over, and the child is perpetually changing anyway, so if you’re worried about negative changes in their face, it’s not the case.

Braces, elastics, headgear, and facemasks all have an effect on the face and lips. But, as orthodontists, we strive to make those changes for the better.

Will the palate expander widen your nose?

YES. Palate expanders will expand the base of the nostrils. Again, we’re talking insignificant numbers here: 2-3mm or less, and we can only measure this change thanks to new 3D techniques. Think of the maxilla as a pyramid. When we turn the expander screw, we widen the base of the pyramid, while the tip is less affected. The tip of the pyramid, in this case, is your nostrils.

The only nose changes I’ve seen were in young children, who need significant expansion, and MARPE patients, since the expansion in MARPE can be so dramatic.

Is having your nose 3mm wider a dealbreaker? Patients suffering from sleep apnea and mouth breathing may disagree. Aside from creating room for teeth, palate expanders also help with better nasal airflow and improved airway, which is a blessing for this category of patients.

Your child may not need maximum expansion, in which case you won’t notice ANY changes in their face or nose. If you’re worried, just take a look at this study – a photographic assessment of 60 children after expander treatment. The vast majority shows absolutely no change in the appearance of their nose.

What happens once the treatment is over?

Once the 4-6 months are up, it’s time to remove the palate expander. We have an entire article on how we remove it and what to expect.

Afterward, there are 3 options:

  • Wear a retainer provided by your orthodontist to maintain results
  • Allow teeth to settle until it’s time for braces
  • Get braces immediately, or even while wearing the expander

If your child had a crossbite, your orthodontist may want to maintain that lateral expansion, so they’ll give your kid a plate-like retainer to wear as much as possible.

Since we tend to overexpand and tip molars toward the cheeks, many orthodontists prefer to allow teeth to settle for a while. I like to leave nature do its thing until it’s time for braces, and teeth often shift into more stable positions.

Since palate expanders are best used between the ages of 8 and 11, many kids don’t have all their permanent teeth in. We’re often still waiting for the canines and second molars. I like to hold off on braces and may only bond them at 12 or even 13 years old, because I believe that the less time your child spends in braces, the better.

If worn for too long, braces can cause demineralization, enamel white spots, cavities and gum disease, so I try to avoid those issues as much as possible.

But some orthodontists prefer to bond braces right away, or even straighten the front teeth as a part of Phase 1 treatment. That’s fine too, and they’ll explain their reasoning when you go over the treatment plan.


Hopefully, you got all the information you need about palate expanders for your kid or yourself. Palate expanders have been studied extensively over the years, and have been proven to be safe, effective, and fast.

All we have to do is get the timing right and make sure it doesn’t come loose. As a recap, here are all the articles we’ve written on palate expanders, to answer all the questions you might have:

Do Palatal Expanders Hurt?
How Is A Palate Expander Removed?
Palate Expander Is Loose
How To Eat With A Palate Expander
When Does Your Child Need A Palate Expander?
Can You Be Too Old For A Palate Expander?
Why Do Palate Expanders Cause a Gap?

And if the answer is not in there, feel free to leave a question in the comments section, or contact me through our contact form. Good luck with your treatment! May you get a nice, big gap!

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