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.

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.

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.