Background: Wala ridge analysis can be used to evaluate the amount of transversal development in the lower arch when the orthodontic treatment is finished. Purpose: To evaluate the lower arch in patients treated with passive and interactive self-ligation systems through Wala ridge analysis. Methods: The study used lower casts of 39 patients who were treated with the Damon, Quick, and In-Ovation systems (13 each) at the CIEO University Foundation in Bogota. Wala ridge of canines, first and second premolars, and first and second molars in initial and final lower casts was analyzed and compared with Andrews reference values (0.6, 0.8, 1.3, 2.0 and 2.2 mm respectively). Results: Measures of final casts of patients treated with the Damon system were 0.4, 0.4, 1.3, 1.9, and 1.8 mm. Measures for the Quick system were 0.4, 0.7, 1.3, 2.0, and 2.0 mm. In the In-Ovation system, measures were 0.2, 0.4, 1.3, 1.9, and 2.0 mm. Conclusion: Transversal development of the arches was achieved with the three systems. However, none of the systems attained the ideal post-treatment values suggested by Andrews, even though the Quick system was the closest.

KEYWORDS
orthodontics; Wala Ridge; transversal development; lower arch; self-ligation brackets