Evaluation of external root resorption during maxillary and mandibular canine retraction at 2, 4, 6 and 8 weeks reactivation intervals using power chain in 1st premolars extraction cases a Randomized Controlled Trial / By Ahmad Fareed Al Mohammad (BDS (2012), Damascus University, Department of Orthodontics, Faculty of Oral and Dental Medicine, Future University in Egypt)

Supervisors : Dr. Nagwa Helmy Al-Mangoury (Professor of Orthodontic, Faculty of Oral and Dental Medicine,Future University in Egypt), Dr. Hend Salah El Sayed (Associate Professor of Orthodontics and Pediatric Dentistry, National Research Centre, Egypt)

Thesis (M. Sc.)-Future university in Egypt, faculty of oral and dental medicine, Department Orthodontics, 2019.

Includes bibliographical reference

Introduction: root resorption is an iatrogenic undesirable consequence of the
orthodontic treatment. The purpose of this study is to evaluate the external root
resorption during maxillary and mandibular canine retraction at 2, 4, 6 and 8
weeks reactivation intervals using power chains. Methods: The sample
consisted of 30 patients (114 quadrants) with bimaxillary protrusion or severe
crowding requiring first premolar extraction. The sample was divided into four
groups. Group I activation every 2weeks, group II activation every 4 weeks,
group III activation every 6 weeks and group IV activation every 8 weeks.
Canine retraction was initiated by extending the power chain from the power
arm to the mini implant in each quadrant with 150 g of force applied. CBCT
was taken for each patient before canine retraction (T0) and after 6 months
(T1).The amount of root resorption assessed by direct vertical measurements of
the canine length at T0 and T1. Results: Group I showed the greatest amount of
root shortening (1.26 mm) while Group IV showed the least amount of root
shortening (0.57 mm). Group III and IV showed (1.08 mm) and (0.72 mm) of
root shortening respectively. There was a significant difference in the means of
root resorption between the four groups [P˂0.001]. Conclusion: Different
periods of power chains reactivation during canine retraction produce varying
amounts of root resorption. According to the results of this study:
1. Root resorption progressively increased with the increase of the reactivation
frequency.
2. The maximum root resorption occurring at the 2 weeks reactivation interval
was within the range reported in previous literature.
3. The more frequent activations of canine retraction will result in an increased
amount of the inflammatory phase of orthodontic tooth movement without an
appropriate healing stage which increases the root resorption process.

Text in English, Abstract Arabic and English