The aim was to compare the rate of teeth movement into fresh and old extraction sites.

Trial design: Randomized controlled clinical trial with a split mouth design. Setting: Jordan University of Science and Technology(JUST) Postgraduate Dental Teaching Clinics and labs.

Participants and interventions: Twenty-eight subjects with bimaxillary proclination requiring extraction of all first premolar teeth participated in this study. In the lower arch, two groups were also identified; group 1 having the first premolar extracted before the commencement of orthodontic treatment and group 2 having the first premolar extracted just before space closure when 0.019 x 0.025 inch SS archwire was reached. Patients were followed-up monthly for three months. At every follow-up visit lower alginate impressions were taken. Extraction spaces in the lower arch follow-up models were measured using digital caliper.

The rate of extraction space closure in the lower arch was assessed monthly.

Inclusion Criteria:

• Age ≥ 16 years
• Proclined upper and lower incisors (Ui/max >115 o, Li/mand >99o)
• Mild upper and lower arch crowding (<4mm) or no crowding
• Need for upper and lower first premolars extraction
• Skeletal I malocclusion (1\

After recruiting patients who met the inclusion criteria, the intervention was randomly allocated to either the right or left side using the permuted random block size of 2 with 1:1 allocation ratio. The random sequences for each intervention to either right or left sides was concealed in opaque envelopes and shuffled before the intervention to increase the unpredictability of the random allocation sequence. Each patient was asked to pick a sealed envelope to assign the intervention to either the right or left side. Allocation concealment was aimed to prevent selection bias and to protect the assignment sequence until allocation.