The aim of the study was to investigate the ability of platelet rich plasma (PRP) to accelerate orthodontic tooth movement in orthodontic patients. The assessed outcomes were rate of canine retraction, total distance moved by the maxillary canines and maxillary first molars. Also, 3-dimentional dentoalveolar assessment including rotation, torque and tipping of maxillary canines and maxillary first molars were performed. Side effects that could be generated from the intervention including periodontal health and root condition were evaluated.The sample was recruited from OutPatients' clinic of the Orthodontic Department, Faculty of Dentistry, Cairo University. The sample consisted of 15 female patients needed maxillary first premolars extraction. In a split-mouth, randomized controlled study, one side was randomly allocated to receive PRP injection with CaCl2 activating solution to serve as the intervention side while the other side received CaCl2 injection only to serve as the control side. After levelling and alignment, 0.017 x 0.025 inch st.st. wire was inserted and canine retraction was performed using NiTi coil springs delivering 150 gm of force. 2 mini-screws were inserted prior to canine retraction to act as indirect anchorage mean. PRP injections and CaCl2 injections were done 0,3,6 weeks. The duration of the study was 4 months. Data were collected from monthly impression and 2 CBCT scans, at the beginning of canine retraction and after 4 months. Assessment of periodontal condition and root resorption was also done. Results were statistically analyzed.Results showed that the total distance travelled by the canines in both sides were similar. The rate of canine retraction was faster in intervention side in the first 2 months with a statistically significant difference in the first month. The rate was significantly slower in intervention side in the third month following stoppage of PRP injections. The canine movement was mainly in the form of controlled tipping. There was minimal anchorage loss though using mini-screws. There was no effect on root condition. Probing depth improved in intervention side. Pain increased following injection in both sides.The following conclusions could be derived from the results of this trial:1. Platelet rich plasma (PRP) had a positive potential to accelerate the rate of orthodontic tooth movement.2. PRP should be injected in the full length of treatment.