Evaluating the Efficacy of the Sliding Mechanisms on Round-section Arch Wire

Evaluation of the Efficacy of Sliding Mechanisms on Round Versus Rectangular Archwires in Canine Retraction After First Premolar Extraction in Class II Malocclusion: A Randomized Clinical Trial

Patients at the Orthodontic Department of the University of Damascus Dental School will be examined, and subjects who meet the inclusion criteria will be included. Then, initial diagnostic records (diagnostic gypsum models, internal and external oral photographs, and radiographic images) will be studied to ensure that the selection criteria are accurately matched.

This study aims to compare two groups of patients with mild to moderate skeletal Class II malocclusion (ANB angle between 5° and 7°), a normal to slightly increased vertical growth pattern (Björk's sum > 390° and < 406°), and an overjet of 5-10 mm. Experimental group: the patients in this group will be treated in the canine retraction phase with a sliding on a round-section archwire of 0.020 inch Control group: the patients in this group. Maxillary canine distalization was carried out using sliding mechanics on a 0.019 × 0.025-inch stainless steel archwire.

Study Overview

• Status: Completed
• Conditions: CLASS II DIVISION 1 MALOCCLUSION
• Intervention / Treatment: Procedure: Round-cross-section archwire; Procedure: Rectangular-cross-section archwire

Detailed Description

In adult Class II camouflage treatment, the extraction of the first premolars is followed by a two-phase retraction protocol, consisting of initial canine retraction and subsequent incisor retraction, which is a standard approach. However, this process often extends treatment duration up to 36 months, creating significant clinical challenges. Prolonged orthodontic therapy not only burdens patients but also increases the risk of complications such as dental caries, root resorption, and periodontal problems, emphasizing the need for more efficient treatment strategies.

To accelerate tooth movement, both surgical and non-surgical methods have been explored. Surgical interventions, including corticotomy, piezocision, flapless cortico-alveolar perforations, and periodontal accelerated osteogenic orthodontics, have shown promising results but remain invasive and less acceptable to patients. Consequently, non-surgical alternatives have gained attention, including low-level laser therapy, electrical stimulation, platelet-rich plasma injections, and mechanical innovations such as self-ligating brackets. Despite these advances, canine retraction remains biomechanically demanding due to its slow rate and the difficulty of controlling unwanted rotation and angulation.

Mechanically, rectangular archwires provide torque control but generate high friction at the bracket-wire interface, delaying canine movement. Round-section archwires, by contrast, reduce bracket-wall contact and friction, enabling smoother sliding mechanics, improved angulation control, and reduced anchorage strain. Despite these theoretical advantages, clinical evidence is scarce. The only notable study, by Hamid, was limited by methodological shortcomings, including a short four-week observation period and a lack of long-term data. Importantly, no clinical trial has systematically evaluated sliding mechanics using a 0.020-inch round archwire, leaving a critical gap in the literature.

• Study Type: Interventional
• Enrollment (Actual): 38
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Syria
  • Rif-dimashq Governorate
    • Damascus, Rif-dimashq Governorate, Syria, DM20AM19
      • Orthodontics Department, Faculty of Dentistry

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Adult patients aged 18-25 years
• Mild to moderate skeletal Class II malocclusion (ANB angle between 5° and 7°),
• A normal to slightly increased vertical growth pattern (Björk's sum > 390° and < 406°),
• An overjet of 5-10 mm.
• A further prerequisite was a camouflage treatment plan involving the extraction of the maxillary first premolars.

Exclusion Criteria:

• the presence of no systemic health issues or any systemic condition known to influence the rate of orthodontic tooth movement,
• active periodontal disease,
• absence of any permanent teeth in the upper arch (excluding third molars),
• crowding of 4 mm or greater,
• inadequate oral hygiene.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Canine retraction on a round cross-section archwire; The patients in this group will be treated by sliding on a round cross-section archwire of 0.020-inch diameter.	Procedure: Round-cross-section archwire; Canines will be retracted on an archwire with a diameter of 0.20 inches.
Active Comparator: Traditional canine retraction on a rectangular-cross-section archwire; The patients in this group will be treated using a sliding rectangular arch wire with a diameter of 0.019 × 0.025 inches.	Procedure: Rectangular-cross-section archwire; Canines will be retracted on an archwire with a diameter of 0.019 x 0.025-inch.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in the Rate of Maxillary Canine Retraction	Canine displacement is measured by projecting the canine apex and the medial end of the third palatal ruga onto the mid-palatal plane; the linear distance between these points is recorded at each time point. Monthly retraction rates are calculated by dividing the change in displacement by the corresponding interval in months. For each subject, mean monthly rates for right and left canines are determined, and the cohort retraction rate is expressed as the average across all patients.	T0: 10 minutes before starting canine retraction stage; T1: 30 days following the onset of canine retraction; T2: 60 days; T3: 90 days following canine retraction onset; TF: At completion of canine retraction (expected to occur within 3-5 months)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Canine Rotation	Canine rotation is defined as the angle between the mid-palatal plane and the line connecting the mesial and distal ridges of the canine crown. The angular shift between consecutive intervals is divided by the interval duration to yield monthly rotation rates. Per-subject averages for right and left canines are computed and then averaged across participants.	T0: 10 minutes before starting canine retraction stage; T1: 30 days following the onset of canine retraction; T2: 60 days; T3: 90 days following canine retraction onset; TF: At completion of canine retraction (expected to occur within 3-5 months)
Change in Anchorage Loss	Anchorage loss is assessed by measuring first-molar movement relative to the third palatal ruga. Linear distances between the maxillary first molar fossa and the medial end of the third palatal ruga, both projected onto the mid-palatal plane, are recorded at T0-TF. Monthly drift rates are calculated similarly to canine retraction, averaged per side, and then across the cohort.	T0: 10 minutes before starting canine retraction stage; T1: 30 days following the onset of canine retraction; T2: 60 days; T3: 90 days following canine retraction onset; TF: At completion of canine retraction (expected to occur within 3-5 months)
Change in Canine Angulation	Canine angulation change is evaluated at T0 and TF via standardized lateral cephalograms. To enhance measurement accuracy, stainless-steel reference wires (0.021 × 0.025 mm; 12 mm apical extension) are affixed to each canine: circular-ended on the right, triangular-ended on the left. Radiographs are analyzed in ImageJ (NIH, USA). Angulation is defined as the angle between each wire and the Sella-Nasion plane.	T0: 10 minutes before starting canine retraction stage; T1: 30 days following the onset of canine retraction; T2: 60 days; T3: 90 days following canine retraction onset; TF: At completion of canine retraction (expected to occur within 3-5 months)
Root Resorption of the Canine	External apical root resorption (EARR) is assessed by comparing maxillary canine root lengths on panoramic radiographs taken at T0 and TF. Baseline root length is recorded at T0; at TF, the reduction in length is measured, and the percentage of resorption is calculated. All measurements are performed in ImageJ (National Institutes of Health, Bethesda, Maryland, USA).	T0: T0: 10 minutes before starting canine retraction stage; TF: At completion of canine retraction (expected to happen within 3 - 5 months)

Collaborators and Investigators

• Sponsor: Damascus University
• Investigators: Principal Investigator: Mohammad N. Kheshfeh, DDS, MSc, Department of Orthodontics, University of Damascus; Study Chair: Mohammad Younis Hajeer, DDS, MSc, PhD, Department of Orthodontics, University of Damascus; Study Director: Ahamd S. Burhan, DDS, MSc, PhD, Department of Orthodontics, Unviersity of Damascus

Publications and helpful links

General Publications

• Mavreas D, Athanasiou AE. Factors affecting the duration of orthodontic treatment: a systematic review. Eur J Orthod. 2008 Aug;30(4):386-95. doi: 10.1093/ejo/cjn018.
• Al-Ibrahim HM, Hajeer MY, Burhan AS, Sultan K, Ajaj MA, Mahaini L. The Efficacy of Accelerating Orthodontic Tooth Movement by Combining Self-Ligating Brackets With One or More Acceleration Methods: A Systematic Review. Cureus. 2022 Dec 23;14(12):e32879. doi: 10.7759/cureus.32879. eCollection 2022 Dec.
• Kusy RP, Whitley JQ. Influence of archwire and bracket dimensions on sliding mechanics: derivations and determinations of the critical contact angles for binding. Eur J Orthod. 1999 Apr;21(2):199-208. doi: 10.1093/ejo/21.2.199.
• Southard TE, Marshall SD, Grosland NM. Friction does not increase anchorage loading. Am J Orthod Dentofacial Orthop. 2007 Mar;131(3):412-4. doi: 10.1016/j.ajodo.2006.09.037.
• Tidy DC. Frictional forces in fixed appliances. Am J Orthod Dentofacial Orthop. 1989 Sep;96(3):249-54. doi: 10.1016/0889-5406(89)90462-9.

Study record dates

Study Major Dates

• Study Start (Actual): July 7, 2023
• Primary Completion (Actual): April 1, 2024
• Study Completion (Actual): July 15, 2024

Study Registration Dates

• First Submitted: November 14, 2025
• First Submitted That Met QC Criteria: November 17, 2025
• First Posted (Actual): November 24, 2025

Study Record Updates

• Last Update Posted (Actual): November 24, 2025
• Last Update Submitted That Met QC Criteria: November 17, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Canine retraction; Sliding mechanics; acceleration of orthodontic tooth movement; Bidimensioanl archwire
• Additional Relevant MeSH Terms: Stomatognathic Diseases; Tooth Diseases; Malocclusion; Malocclusion, Angle Class II
• Other Study ID Numbers: UDDS-2025-Ortho-10

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No