RESUMO
Objective:To evaluate the changes in the transverse dimension and the perimeters of the maxillary archs produced by 3 self-ligating appliance systems during the leveling and aligning phases. Methods: 45 patients who had class I skeletal pattern and upper arch crowding 3-6 mm were divided into 3 groups with 15 subjects in every group. The dental casts were analyzed. Results: Statistically significant increases were recorded of all dentoalveolar widths (with the exception of intermolar width measured lingually) and arch perimeters. The increase in arch perimeter showed a significant negative relationship with the individual perimeter of the maxillary arch before treatment. No significant change was found in arch depth. Conclusion: The self-ligating appliance systems produce statistically significant increases in the transverse dentoalveolar width and the perimeter of the maxillary arch during the leveling and aligning phases of treatment.