A palatal expander widens your upper jaw by gradually separating the two halves of the palate along the natural seam (called the midpalatal suture) that runs down the center of the roof of your mouth. This creates more space for crowded teeth, corrects bite misalignment, and can improve breathing. The device is most commonly used in children and adolescents, though adults can also undergo expansion with additional procedures.
How an Expander Widens the Jaw
Your upper jaw isn’t a single solid bone. It’s actually two bones joined by a strip of flexible tissue running front to back along the center of your palate. An expander sits on the roof of your mouth, anchored to your upper back teeth, and applies gentle outward pressure on both sides. This pressure slowly pulls the two halves apart, and new bone fills in the gap over time.
Rapid palatal expanders can widen the jaw at a rate of about 0.5 millimeters per day. You or a parent activate the device by inserting a small key into a central screw and turning it, typically once a day. Some treatment plans call for turns once every other day or twice a week, depending on how much expansion is needed and how quickly the orthodontist wants to move. Each turn nudges the two halves of the palate a tiny bit further apart.
What Problems It Corrects
The most common reason for an expander is a crossbite, where the upper jaw is too narrow and the top teeth sit inside the bottom teeth when you bite down. Left untreated, a crossbite can cause uneven jaw growth, wear down teeth, and lead to chronic jaw pain.
Expanders also address crowding. When the upper arch is too small to fit all the permanent teeth, widening the palate creates room and can reduce or eliminate the need to extract teeth later. In some cases, a narrow palate contributes to breathing problems by limiting airflow through the nasal passages. Widening the jaw can open the nasal cavity and improve airflow, which is why expanders are sometimes part of treatment for children with mouth-breathing habits or sleep-disordered breathing.
Why Age Matters
Expanders work best when the midpalatal suture is still flexible. This suture typically begins to harden between ages 15 and 18 and can be fully fused anywhere between 25 and 35. That’s why most patients get expanders during childhood or early adolescence, when the bone is still responsive to pressure.
That said, the timeline varies a lot between individuals. Research has found that all stages of suture maturation can appear as early as age 11, while some adults in their 30s, 50s, and even 70s show no complete fusion. Chronological age alone is not a reliable predictor. Orthodontists increasingly use 3D imaging (CBCT scans) to evaluate the actual state of the suture before deciding on a treatment approach.
For adults whose suture has already fused, a standard expander won’t work on its own. In these cases, a surgeon makes small cuts in the bone to release the suture before the expander is activated. This procedure, called surgically assisted rapid palatal expansion (SARPE), allows adult patients to achieve the same widening that children get from the device alone.
Types of Expanders
The two most common designs are the Hyrax and the Haas. Both attach to the upper molars and use a central screw that you turn to generate outward force. The key difference is that the Haas type includes acrylic pads that rest against the roof of the mouth, distributing force between the teeth and the palatal vault. The Hyrax type is all metal, delivering force primarily through the teeth it’s attached to. This makes the Hyrax easier to keep clean since food and bacteria are less likely to get trapped.
Despite the design differences, clinical studies comparing the two have found no significant difference in the skeletal results they produce. Your orthodontist will choose based on your specific anatomy and treatment goals.
What to Expect During Treatment
The active expansion phase, where you’re turning the screw regularly, usually lasts about six weeks. During this time, you’ll likely notice pressure in the roof of your mouth, around your nose, and sometimes between your eyes after each turn. This typically fades within 15 to 30 minutes.
One of the most noticeable side effects is a gap that opens between your two front teeth. This is actually a good sign. It means the two halves of the palate are separating as intended. The gap can look alarming, but it tends to close on its own during the stabilization phase. As the expanded tissue settles, the stretched gum fibers pull the front teeth back together, and many patients find the gap has completely closed by the time the expander comes out.
After active expansion stops, the expander stays in place for several more months while new bone fills in the widened suture. Total treatment time, including this stabilization period, ranges from three to six months for most patients, though some wear the device for up to a year. Removing it too early risks the palate narrowing back to its original width.
Eating, Cleaning, and Talking
The first few days with an expander are the hardest. Speaking feels awkward because your tongue has to work around a metal appliance sitting where it normally rests. Most people develop a temporary lisp, especially on “s” and “sh” sounds. Reading aloud or just talking more than usual helps your tongue adapt faster, and most patients sound normal within a week or two.
Eating requires some adjustments. Sticky foods like gum, taffy, and caramels can pull the expander loose or get wedged in the mechanism. Hard foods like ice, nuts, and popcorn risk bending the metal or breaking the appliance. Raw fruits and vegetables like whole apples, carrots, and celery should be cut into small pieces rather than bitten into.
Hygiene around the expander takes extra effort. Food collects easily on and around the device, especially in the space between the acrylic or metal and the roof of your mouth. Rinsing with water after meals helps dislodge trapped food, and a water flosser or syringe can flush out debris from hard-to-reach areas. Thorough brushing around the bands where the expander meets the teeth prevents decalcification and cavities during the months the device is in place.
After the Expander Comes Out
Once the orthodontist confirms that enough new bone has formed to hold the expansion, the device is removed. This is usually painless and takes just a few minutes. Many patients transition directly into braces or aligners at this point, since the expander created the space needed for teeth to move into proper alignment. The palate itself is permanently wider once the bone has fully mineralized, so the results of expansion are stable long-term as long as the retention phase was completed.