Maxillary transverse deficiency may be congenital or acquired and can cause uni-lateral or bi-lateral cross-bites and crowding due to space deficiency.
Skeletal correction by force application to maxillary halves and separate them is possible before 15 years old. Traditionally, force applied through dentition and this causes inadvertent tooth movements and its side effects such as buccal tip, gingival recession, buccal cortex bending and perforations, decrease of skeletal correction and increase of relapse possibility. The more increase in age, the more anatomic resistance and so the more severe side effects occur. In adults, maxillary expansion should be done by surgical segmentalization that has most relapse potential among all orthognathic procedures. A good alternative is surgically assisted rapid maxillary expansion (SARME). In this technique, expansion is facilitated by osteotomy of anatomic resistances. Even in this approach force application through dentition may produce the same side effects too. Recently, it has been tried to apply force directly to the maxillary bone.In this paper current bone-borne maxillary expansion appliances are reviewed.