This aim study aims to compare clinical effectiveness of customized lingual brackets and conventional labial brackets in alignment period in a sample of Class I malocclusion patients treated on a nonextraction basis.

The study included 20 patients who presented with Class I malocclusion and scheduled for orthodontic treatment without tooth extraction. The patients were randomly assigned for treatment with customized lingual brackets or with conventional labial brackets. During the alignment period 0.012 inch (T1) , 0.014 inch(T2), 0.016 inch (T3)NiTi arch wires were performed respectively and the control visits were scheduled by 6-weeks intervals. In all sessions, digital models were obtained by intra-oral scanning device after removal of arch wire, which then analyzed by software. In order to analyze change in T0 (pretreatment), T1, T2 and T3; Little's irregularity index, distance between canine teeth, distance between first premolar teeth, distance between second premolar teeth, distance between first molar teeth and arch length measurements were performed on digital models.

Inclusion Criteria:

• Class I malocclusion
• Completed permanent dentition
• Crowding ≥ 6 mm

Exclusion Criteria:

• Tooth loss or extraction except third molars
• Having cross bite
• Having genetic or hormonal disorder
• Using a chronic drug
• Previous orthodontic treatment and prosthetic restoration
• Inappropriate oral hygiene and periodontal diseases