The palatal expander is attached to the upper molars through bonding or by cemented bands. It is an orthodontic device used to create a wider upper jaw and is typically used when the upper jaw is too narrow for the lower jaw or when the upper teeth are crowded or blocked out of the dental arch. When patients are still growing, the connective tissue between the left and right halves of their upper jaw is very responsive to expansion. Application of outward pressure is able to widen the upper jaw by triggering an increased amount of bone to grow between the right and left hales of the jaw, ultimately resulting in an increased width.