Abstract: To evaluate changes in the maxillary dentoalveolar and dental arch produced by the In-Ovation self-ligating system during the leveling and aligning phases of treatment. MethodsThe In-Ovation self-ligating system was used in 20 patients (13 females and 7 males, 17 to 35 years old) with mild crowding in the maxillary arch to level and align the maxillary dentition. Dental casts of the maxillary arch were taken at T1(immediately before treatment)and T2(at the end of leveling and aligning phase with 0.016in Ni-Ti archwires). All dental casts were scanned by a special laser scanner and treated with Image ware software to install digital models, and then many landmarks of dentoalveolar and dental arch were selected in the digital models. All data were analyzed by SPSS12.0 software, and changes before and after treatment in dentoalveolar and the dental arch widths, and the depth and perimeter of the maxillary arch were determined. ResultsCompared with T1, statistically significant increases were recorded in all dentoalveolar and dental arch widths, except for the intermolar width measured fossa， and also arch perimeter at T2 (P＜0.05). No significant changes were found in the arch depth. ConclusionDuring the initial phase of leveling and aligning, the In-Ovation selfligating system produces significant increases in the transverse dentoalveolar, the dental arch width and the perimeter of the maxillary arch.

Key words: Self-ligating brackets, Arch width, Arch depth, Arch perimeter