Inclusion Criteria:  Class I malocclusion with severe crowding (more than 5 mm of tooth-size-arch-length-discrepancy). Good oral hygiene and periodontal health. No congenitally missing or extracted teeth (except for the third molars). No history of previous trauma to the maxillofacial region or surgical interventions.  Exclusion Criteria:  Previous orthodontic treatment. Subject with psychological abnormalities. Subject with systemic diseases. Subject has known allergy to latex and plastic