Inclusion Criteria:  Sever crowding greater than 6 mm on the upper jaw in which orthodontic treatment requires extraction of two upper premolars. The Little's Index of Irregularity is more than 7 mm. Good oral health (plaque Index is less or equal to 1). Class I or class II (ANB ≤ 5) or class III (ANB ≥ 0). Overbite is between 0-4 mm. No skeletal constriction on the upper jaw. No congenitally missing or extracted teeth (except for the third molars).  Exclusion Criteria:  Any systemic diseases affect teeth movement. Any congenital syndromes or cleft lip and palate. Bad oral health. The patient is not committed to periodic follow-up times.