Usage The Bonded Palatal Expansion Appliance is used to slowly and carefully broaden the upper jaw by exerting lateral pressure on the two halves of the maxilla (upper jaw) in patients with a constricted maxilla (narrow upper jaw). If done properly, bone grows in the middle and a once-constricted maxilla can attain proper width to improve the bite. Expanding the maxilla may also help to create space for eruption of permanent teeth.