How to Activate an Arch Expander (RPE, MARPE, MSE)

Arch Expander, Yonsei Jeongwon Dental Clinic

Hello! I am Yoon Jeong-won, the chief director of the orthodontic clinic in Daechi-dong.

While looking into orthodontic treatment, have you ever heard the term arch expander? An arch expander, or Rapid Palatal Expander (RPE), is literally a device that expands the arch. So why do we need to expand the arch? If the upper jaw is narrow, the teeth may not be aligned properly and bite problems can occur. The device used in this case is the arch expander.

Why is an arch expander needed?

If the upper jaw is narrow, there is not enough space for the teeth to align properly, so the teeth may overlap or become crooked. Also, if the upper jaw is narrow, the bite between the upper and lower jaws may not match, which can cause a crossbite. In addition, when the upper jaw is narrow, the space for breathing becomes smaller, increasing the likelihood of mouth breathing.

Lack of space for tooth alignment

Molar crossbite

In this case, if the upper jaw is widened using an arch expander, it can create space for the teeth to align.

Midpalatal Suture (정중구개봉합)

The upper jawbone is not completely fused in childhood and is weakly connected by a suture called the midpalatal suture. By gradually separating this suture, the width of the upper jawbone can be increased. It is mainly used in growing children and adolescents, but in recent years it has also been widely used in adults.

In children and adolescents who are still growing, expansion of the upper jawbone occurs relatively easily. However, in adults whose growth plates have closed, expansion can be achieved with the help of miniscrews (MARPE, Miniscrew-assisted RPE, or MSE, Maxillary Skeletal Expander).

RPE (Rapid Palatal Expander)

MARPE (Miniscrew-assisted RPE)

MSE (Maxillary Skeletal Expander)

How do you activate an arch expander?

Because arch expanders are mainly used for growing children and adolescents, in most cases parents are the ones who turn the arch expander. However, finding the small hole in a small, dark mouth and turning the device is not easy. Sometimes, even after receiving a sufficient explanation from the clinic on how to turn the device, patients return to the hospital because they have difficulty activating it themselves at home.

So today, I would like to explain how to activate an arch expander with photos and a video!

RPE/MARPE vs MSE

RPE/MARPE and MSE are both arch expanders. If you look at the device design in the photos above, you can see that both devices have an arrow pointing downward (the part indicated by the blue triangle), and the left device has a hole while the right device has a hexagonal post (the part indicated by the red triangle).

When turning the device, insert the tool into the part indicated by the red triangle and push the instrument in the direction of the arrow indicated by the blue triangle. That may not be very easy to understand, right? Let me explain a little more with the photos below.

How to activate RPE/MARPE

How to activate RPE

How to activate RPE

As explained earlier, insert the activation key into the front hole. At this time, the tip of the key must be inserted all the way to the end of the hole. After fully inserting the key, push it inward toward the inside of the mouth until it can no longer move, as if a hinge were folding. In the second photo, the next hole appears in the area indicated by the red triangle. If it is turned correctly, seeing the next hole like this means the device has been activated properly. When removing the key, do not pull it forward; instead, push it backward while removing it so that the activated position is maintained as you take the device out. If you watch the video, you will be able to understand it more easily.

The next video shows the sensation of actually inserting the activation key into the mouth from the front of the patient and turning the device.

How to activate the MSE expander

How to activate MSE

The MSE expander is turned a little differently from RPE. While the RPE expander is activated by inserting the key into the hole and turning it once, MSE is activated by fitting the wrench onto the hexagonal post and pushing it firmly in the direction of the arrow. One thing to note, however, is that, as shown in the photo, the wrench is small, so you should attach it to the blue rubber ring included with the device before using it. If you try to turn it without doing so, the wrench may accidentally fall into your mouth, so I strongly recommend using it with the blue rubber ring attached.

Difference between how to activate RPE and MSE

An arch expander is a process of gradually widening the teeth and bone each day, so it is very important to activate the device correctly. If the arch expander is overactivated or delayed, bite imbalance, damage to periodontal tissues, and discomfort may occur, so it is important to strictly follow the prescribed schedule.

If discomfort or pain occurs during use, do not force it; it is safer to consult your dentist right away. Also, food often gets trapped around the device, so don't forget to maintain thorough oral hygiene!

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