Evaluation of Effects of Bracket's Slot System on the Quantity and Quality of Teeth Movements During Orthodontic Leveling and Alignment Stage

Inclusion Criteria: * An age range from14 to18 years. All permanent teeth are erupted(3rd molar not included). * Angle class I malocclusion with normal facial proportions. * Moderate to severe crowding in the lower dental arch asassessed by lett irregularity Index that require treatment with fixed appliance using extraction approach. * There is no previous orthodontic treatment. Exclusion Criteria: * Poor oral hygiene or periodontally compromised teeth. * Craniofacial anomalies or previous history of trauma, bruxism, or Parafunctions. * Uncooperativepatient.