This study aims to investigate and compare the effect of PRF and vitamin Dꝫ injections on root resorption by using CBCT

• Participants will be recruited from the Faculty of Dentistry, Beni-Suef University. All subjects will be informed of the treatment procedures and will sign a consent form.
• Subjects will be randomly divided into two groups:

Group 1 (PRF group): upper canine retraction will be facilitated by PRF injection that will be randomly assigned to one side (experimental side). The contralateral side will serve as the control one.

Group II (Vitamin Dꝫ group): canine retraction will be facilitated by Vitamin Dꝫ injection that will be randomly assigned to one side (experimental side). The contralateral side will serve as the control one.

• The predicted sample size (n) was a total of (28) cases (i.e. 14 cases per group). Sample size calculation was performed using G*Power version 3.1.9.7
• Randomization:

Simple randomization will be designed with the aid of a computer-generated schedule with 1:1 allocation ratio. Allocation concealment will be achieved using identical opaque, sealed envelopes. Randomization and allocation concealment will be performed by one of the academic staff who will not be involved in the study and will keep the allocation table away from the operators. The operator will shuffle the sealed envelopes and will ask the patient to pick one envelope at the time of recruitment. In each group, a randomly selected side will act as the experimental side while the contralateral side will serve as the control. Blinding of the operators will not be applicable and so blinding will be limited to the outcome assessment.

- Methodology: All patients will be treated with a 0.022-inch MBT bracket system. Leveling and alignment phase will be completed until a 0.017 X 0.025'' stainless steel wire will be inserted passively into the bracket slot. Before canine retraction, the subject will be randomly assigned to one of the groups (PRF or Vitamin Dꝫ group). In both groups, canine retraction will be performed with closed Ni-Ti coil springs with a force of 150 g per side that will be adjusted by the use of a force gauge.

IInclusion criteria:

1. Age: 18- 40 years old.
2. Angle Class I or Class II dental malocclusion that required bilateral maxillary first premolar extraction and upper canine retraction as a part of the treatment plan.
3. Good to fair oral hygiene.
4. Normal probing depth.

Exclusion criteria:

1. Active periodontal disease.
2. Poor oral hygiene.
3. Systemic diseases or medications that alter bone metabolism or tooth movement.
4. Craniofacial anomalies

Single-blinded limited to the outcome assessment