A palatal expander, also known as a rapid palatal expander, rapid maxillary expansion appliance, palate expander or orthodontic expander, is used to widen the upper jaw so that the bottom and upper teeth will fit together better.

Although it may vary from person to person, most usually feel slight pressure on their teeth. As the patient turns the expansion screw using the key, a space develops between the front two teeth. Some may notice a larger space while others do not notice a space at all. It usually takes several days to adjust to eating and speaking after first receiving the rapid palatal expander. Patients may experience pain and headaches while wearing palatal expanders and when the screw is turned. They may also feel a sore on their tongue from contact with the expander’s metal bars.