الفهرس 
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Abstract
Orthodontics has been developing greatly in achieving the desired results both clinically and technically. Nowadays, it is still very challenging to reduce the duration of orthodontic treatments. It is one of the common challenges that faces orthodontist as long duration of treatment causes irritation of tissues, increasing risks of caries, gingival recession, and root resorption. A number of attempts have been made to create different approaches both preclinically and clinically in order to achieve quicker results, but still there are a lot of uncertainties and unanswered questions towards most of these techniques. Most attempts can broadly be categorized into biological, physical, biomechanical, and surgical approaches.
The study was conducted on ten rabbits using split mouth technique. Both quadrants of the upper jaw of each rabbit will be used. The upper left quadrant will be the control side and upper right quadrant will be the side of injections. The study side was injected intraligamentary with PGE2 and vitamin D to assess their effect on OTM.
The orthodontic appliance will be composed of a 5 mm long NiTi closed coil spring. The closed coil spring will be connected posteriorly to the first molar and anteriorly to the incisor by a ligature wire. The ligature wire will be fixed to teeth by composite bonding material. Force of 60 gram will be applied.
The animals were sacrificed after 21 days. The right and left jaw halves of the ten animals were prepared for specimen. The specimens were decalcified and prepared for histological evaluation to detect changes in osteoblastic and osteoclastic activity.
The collected data were then statistically analyzed for changes and compared to the differences between before and after treatment.
from the results of this study, it could be concluded that:
o The average of tooth movement in study side was 1.43 ± 0.13 mm while in control side was 0.66 ± 0.10 mm. There was a significant statistical difference between two sides (p- value <0.0001)
o The tension side showed increaseing in thickness in the bony part, periostum and the periodontal ligament
o Activation and proliferation of osteoblasts which differentiated from the periostum and have the tendancy to form haversian system.
o Semi-thin section as well as ultrathin section of alveolar bone studied with electron microscopy revealed the presence of periostum formed by dens fibrous connective tissue.
o The pressure side of the tooth of the treated group showed compression of the periodontal ligament, periosteum and compacted bone with congestion of the vasculature
o Thus, the combination Vitamin D+PGE2 is useful and there is a synergistic effect with Vitamin D and PGE2.