RPE Orthodontics: How the Expander Turns and How Long It Takes

A rapid palatal expander (RPE) widens a narrow upper jaw by gently separating the two halves of the palate at their midline seam. It attaches to the back upper teeth, and a small central screw is turned with a special key according to your orthodontist’s instructions.

If you’re holding that key for your child, follow the prescribed schedule rather than judging progress by how tight the appliance feels. Extra turns can put more force on the teeth and appliance than planned.

What is the expander attached to before you touch the key?

The appliance sits in the roof of the mouth and is anchored to the back upper teeth. Force from the screw travels through these attachments to widen the upper jaw. Cleveland Clinic describes the expander as fitting in the roof of the mouth and attaching to the back upper teeth for stability.

A loose band or bent wire needs attention, even if you can still turn the key. If an attachment comes loose or a wire is poking, call the office that placed the expander rather than trying to adjust it at home.

How does one turn of the key widen the upper jaw?

The palate has two halves joined by a suture, the seam where they meet. The screw works like a small jack, pushing those halves apart a little at a time. As expansion progresses, the body responds by building new bone to fill the space left behind. Each prescribed turn adds to that gradual movement.

What the screw does

Turning the screw adjusts the width of the appliance. Your orthodontist sets the amount and frequency of those adjustments; a general turning schedule is not a substitute for your child’s instructions.

Tightness and mild tenderness can occur, especially during the first few days or after a turn. Severe pain is not expected and should be reported to the treating office.

Turning the key, step by step

Have the office demonstrate the technique before you try it at home. These checks support that demonstration, but the instructions for your child’s appliance come first.

1. Seat the key fully. Insert it into the screw as demonstrated. A partly inserted key can slip.
2. Confirm the direction. Follow the arrow or the direction shown in the office instructions. Turning backward can reverse an adjustment.
3. Record each completed turn. Use a calendar or written log so another caregiver can see what has already been done.
4. Turn only the prescribed amount. Stop after the adjustment the office instructed, even if the screw could turn farther.
5. Stop if something feels wrong. If the key is hard to turn or the expander feels loose, do not force it. Call the treating office.

How long does widening usually take, and why does it vary?

Cleveland Clinic (updated June 30, 2022) cites about 0.5 millimeters per day for rapid expanders and says most people reach the desired result in three to six months. That daily figure describes expansion during active treatment, not a rate to multiply across every day the appliance stays in place.

The same source notes that treatment often begins at age 7 or 8. Older patients may need longer, sometimes up to a year, because their bones are more developed. Age alone does not determine which appliance will work; the orthodontist also evaluates skeletal maturity.

Ask for two timelines.

First, how long active turning is expected to last. Second, how long the appliance may stay in place afterward. Those are different stages, and your child’s progress at follow-up visits determines when to move from one to the next.

Why does a gap appear between the front teeth?

A gap can appear between the upper front teeth as the two halves of the palate separate. This is an expected part of expansion, not something you need to close or correct at home.

The gap alone does not tell you when to stop turning. Your orthodontist checks the bite and the amount of widening before changing the schedule. Keep following the prescribed plan unless the treating office tells you otherwise.

What should you do if a turn is missed?

Do not double the next adjustment.

An extra turn can place more force on the teeth and appliance than your orthodontist intended.

• Call the office that placed the expander.
• Tell them which day or adjustment was missed.
• Follow their instructions about when to resume.

If more than one person helps with turns, keep the log beside the instructions. Checking it before each adjustment helps prevent an accidental repeat.

What happens after the width is reached?

Active turning stops when your orthodontist confirms that the planned width has been reached. The appliance usually stays in place afterward to hold that width while new bone fills the space. Your orthodontist also handles removal; it is not a home procedure.

Ask how expansion fits into the rest of your child’s treatment and what will hold the result afterward. The appliance-holding phase and later retainer care have different roles. You can learn about retainers through orthodontic retention at Markowitz Orthodontics.

Where should you ask about your child's turns?

If you are unsure about the turning technique, ask for an in-person demonstration with your child’s appliance. At Markowitz Orthodontics, our two offices are in Blue Bell and Narberth, which is our Lower Merion location. Call Blue Bell at (215) 367-5385 or Lower Merion at (610) 667-6770.

To request a visit, use our Appointment Request form. Our palatal expander service page explains the appliance, and you can find office details on the Blue Bell location or Lower Merion location page.

Frequently asked questions

What does RPE mean in orthodontics?

RPE stands for rapid palatal expander, an appliance that widens a narrow upper jaw by separating the two halves of the palate along their midline seam. A conventional RPE attaches to the back upper teeth and uses a central screw for adjustments. Our palatal expander page explains its use and care.

What is the difference between rapid and slow maxillary expansion?

Both widen the upper jaw, but they use different treatment schedules and may use different appliances. Rapid expansion makes adjustments more frequently; slow expansion widens the jaw more gradually. The orthodontist chooses an approach based on the patient’s growth and the correction needed, rather than speed alone.

Is an expander necessary before braces?

No, an expander is not needed before every braces treatment. It may be recommended when a narrow upper jaw affects the bite or contributes to crowding. Cleveland Clinic’s June 2022 patient guide lists crossbite and difficulty chewing among the reasons for expansion, but an examination is needed to determine whether it is appropriate for your child.

How much does a palate expander cost?

The fee depends on the appliance and your child’s case, so ask the office for an individual estimate. Ask whether the estimate includes follow-up visits and the period when the appliance stays in place after turning stops. Our financial information page is a starting point for payment and insurance questions, and any coverage needs to be confirmed for your plan.