Introduction:The purpose of this study was to evaluate the dental changes after expansion via memory palatal expansion screw device in adolescent patients having posterior crossbite. Material and Methods: The study was conducted on 10 patients (ages, 13.5 ± 1.1years) who had posterior crossbite. All patients were treated by the memory palatal expansion screw device. CBCT images were taken before and immediately after expansion. Results:The results revealed significant increases in the transverse dentolinear measurements (P≤0.05). The transverse dentoangular measurements (the outer angle) decreased significantly (P≤0.05). There were insignificant changes at the vertical position of the upper first permanent molars (P>0.05). Conclusion : The maxillary arch has been effectively expanded coronally and apically, and  all anchored teeth were significantly buccal tipped .