**1. Introduction**

An adequate transverse maxillary dimension is a critical component of a stable and functional occlusion. [1] Orthopedic rapid maxillary expansion in skeletally immature patients is the procedure of choice to correct this condition in that age group. However, as skeletal maturity approaches, bony interdigitation increases as the sutures fuse. [2,3] After suture closure or completion of transverse growth, orthopedic transverse maxillary expansion is largely unsuccessful because the expansion is primarily composed of no basal skeletal movement. [4] This phenomenon leads to difficulty separating the maxilla with orthopedic forces alone and bending of the alveolus, dental tipping and minimal maxillary expansion. The result is relapse despite overcorrection, periodontal defects, and malocclusion. [5]

Rapid maxillary expansion can produce unwanted effects when used in a skeletally mature patient, including lateral tipping of posterior teeth [6,7], extrusion [8-10], periodontal mem‐ brane compression, buccal root resorption [11-13], alveolar bone bending [7], fenestration of the buccal cortex [13-16], palatal tissue necrosis [17], inability to open the midpalatal suture, pain, and instability of the expansion [7,10,18-20]. Several reasons have been speculated regarding factors that limit orthopedically induced maxillary expansion in skeletally mature patients.

However, a few reports in the literature contradict these findings and state that nonsurgical maxillary expansion is as successful in adults as it is in children [21, 22]. Experiencing more complications, after attempts to orthopedically alter the transverse dimension of the maxilla with advancing age, surgical procedures have been recommended to facilitate correction of transverse discrepancies by Perrson [23], who found evidence of bony union at 17 years in the midpalatal suture. Burston [24], however, found no evidence of synostosis in the same suture by the age of 18 years.

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