Effects of Injectable platelet rich fibrin (i-PRF) on reduction of relapse after orthodontic tooth movement: Rabbits model study.

OBJECTIVES: The objective of this study is to determine whether submucosal local injection of i-PRF may affect orthodontic relapse by increasing bone density, which further leads to reducing orthodontic relapse. MATERIALS AND METHODS: Forty-five adult male albino rabbits were randomly divided into three groups: group I (control) with 15 rabbits injected with 200 µl of phosphate-buffered saline (PBS), group II with 15 rabbits injected with 200 µl of i-PRF, and group III of 15 rabbits inject with 400 µl of i-PRF. The lower incisors of rabbits moved distally by a modified orthodontic appliance for 2 weeks; then, the appliance was maintained in position to retain the gaining space for 2 weeks. During the retention period, each group was injected with the specific drug every 7 days. After the retention period, teeth were allowed to relapse by removal of the orthodontic appliance. The results were evaluated by measuring the amount of orthodontic relapse and bone density. The statistical analysis performed by ANOVA and Duncan (P < 0.05 was considered significant). RESULTS: I-PRF groups showed a significant reduction in the amount of relapse at 10, 13, 17, and 20 days compared to the control group, indicated by the highest percentage of relapse for the control group at the end of the study (20 days); it was (90.4%) in compared to lowest percentage of relapse for i-PRF groups-they were 61.2% and 59.9%, respectively. CONCLUSION: Results indicated that i-PRF has the potential to enhance the stability of teeth after orthodontic tooth movement and could have the ability to reduce relapse, probably by increasing the alveolar bone density.

Influence of different orientations and rates of bidirectional distraction osteogenesis of the mandibular corpus: a three-dimensional study

Objective: The objective of this study was to evaluate the biomechanical effect of mandibular corpus distraction osteogenesis with different orientations and rates. Materials and Methods: A three-dimensional model of the mandible was created. The vertical surgical cut was made, the force was applied horizontally in a bidirectional manner within two orientations: parallel to the occlusal plane and parallel to the inferior border of the mandible with three rates (0.5mm, 1mm and 1.5mm). Results: The maximum values for von Mises stress when the force was applied parallel to the inferior border of the mandible with all three rates were smaller than those with force direction parallel to the occlusal plane. The displacement in all three directions x, y, and z were not parallel and prominent in the anterior part of the mandible, while the movement at the posterior part is negligible, x and z displacement were bigger when force was applied parallel to the inferior border of the mandible, z displacement was more prominent than x and y displacement, both directions produced upward rotation of the mandible, this rotation was more noticeable when the force was applied parallel to the inferior border of the mandible. Conclusions: A vertical cut can be used in the patient with a long anterior face. This site of distraction achieves more lengthening of mandible than expansion.