NCT02996292.

Methods	Setting: Syrian Arab Republic Design: 3‐arm parallel RCT No. of centres: unclear Study duration: unclear
Participants	Age 14‐24 years Inclusion criteria: Permanent dentition stage Crowding up to 6 mm Class I relationship Good oral hygiene Exclusion criteria: Poor oral hygiene Previous orthodontic treatment Patients with syndromes, clefts, or craniofacial abnormalities Class II or III skeletal anteroposterior relationship Crowding < 3 mm and > 6 mm
Interventions	Orthodontic intervention: fixed appliances Conventional brackets versus active self‐ligating brackets versus passive self‐ligating brackets
Outcomes	Primary outcome: speed of alignment Secondary outcomes: Changes of the torque and tipping of teeth Changes of widths and depths of the dental arches External apical root resorption
Notes	Emailed author; awaiting contact