Maxillary expansion with a Rapid Palatal Expander (RPE) is an orthodontic treatment designed to widen the upper jaw. This procedure involves attaching an expander device to the upper molars and gradually expanding it using a key over a period of several weeks. It is primarily used to correct a narrow upper jaw, which can lead to issues with bite and teeth alignment. Although this treatment is most effective during childhood or adolescence, when the jaw is still growing, it can also be performed on adults. The procedure is generally well-tolerated and can lead to benefits such as improved breathing, speaking, and chewing, as well as a more symmetrical facial appearance.