Evaluation of incisors position following anterior segment retraction using friction versus frictionless mechanics: A randomized clinical trial / By Dorra MHD Izzat Bakhit, BDS Future University in Egypt (2015)

Supervision of Dr. Yehya A. Mostafa, Professor and Chairman, Department of orthodontics and dentofacial Orthopedics, Faculty of Oral and Dental Medicine, Future University in Egypt, Dr. Fouad A. El Sharaby, Associate Professor of Orthodontics and Dentofacial Orthopedics, Department of orthodontics and dentofacial Orthopedics, Faculty of Dentistry, Cairo University, Dr. Heba M. Dehis, Lecturer of Orthodontics and Dentofacial Orthopedics, Department of orthodontics and dentofacial Orthopedics, Faculty of Dentistry, Cairo University

Thesis (M.Sc.)-Future University, Faculty of Oral and Dental Medicine, Department of Orthodontics, 2020.

Includes bibliographical references.

The aim of the current study was to investigate the incisors position following anterior segment retraction using friction or frictionless mechanics. Other outcomes were also investigated like rate of retraction, anchorage loss, root resorption and pain. The previously mentioned outcomes were assessed using digital models for upper anterior segment retraction rate and CBCT for the other outcomes.
Statistical calculation of the sample size revealed the need of 15 patients per group (considering drop out) in order to reject the null hypothesis. A total of 30 patients requiring 1st premolar extraction and retraction were recruited.
Preparation phase started by bonding the fixed appliance, leveling and alignment stage, then miniscrews insertion between the 2nd premolars and 1st molars in all arches in ensure proper anchorage control before 1st premolars extraction. After extraction was done, separate canine retraction was performed. Patients were then referred for the uptake of a pre-retraction CBCT (considered T0) as well as impressions were taken. Next, Patients were randomly allocated to one of the intervention mechanics, either friction or frictionless.
If a patient was assigned to Group1 (friction), 8 mm crimpable hooks were attached to the 0.017 x 0.025” stainless steel wire and power chains, delivering 160g of force, attached to the mini-screw. While if a patient was to Group2 (frictionless), T-loops were fabricated on 0.017x0.025” TMA wire, according to Burstone’s dimensions and 4mm activation provided 160g of force. The posterior segments were consolidated on a 0.017x0.025” stainless steel wire with the canine attached to the mini-screw via a twisted ligature wire.
Follow up procedure was at 4 weeks interval, where re-activation of the intervention and impression taking was done. The final records for each participant were taken when the following criteria were achieved, canine ClassI, normal overjet and lower extraction spaces closure. After drop-outs, twenty patients were then sent for the uptake of the final CBCT (after 6 months) and final impressions were also taken.
From the data measured and the results produced within the limitation of this study, the following can be concluded:
1- There is no advantage of frictionless mechanics over the friction mechanics in regards to incisors position in 3D measurements of tip, torque and vertical changes.
2- Insignificant differences between the average rate and duration of anterior segment retraction between the two mechanics.
3- Frictionless group’s anchorage loss was more significant than the friction group.
4- Root resorption was detected but no significant difference between the two groups.
5- Pain scores were worst at the beginning of the interventions then declined. Yet, no significant difference between the two groups.

Text in English, abstracts in English and Arabic.