Comparative Evaluation of Frictional Resistance Among Passive Self-Ligating Brackets with Stainless Steel Arch wires - An In vitro Study

Introduction: Friction at the bracket–archwire interface significantly influences sliding mechanics in orthodontics. Self-ligating brackets are designed to minimize friction and improve treatment efficiency. This study compared the kinetic frictional resistance of three passive self-ligating systems—Damon, Smart Clip, and Selfy—with stainless steel archwires. Materials and Methods: A total of 160 brackets (0.022-inch slot) were tested, equally distributed into Damon (n = 40), Smart Clip (n = 40), Selfy (n = 40) and Conventional stainless steel brackets (n = 40) groups. Each was evaluated with 0.019 × 0.025-inch stainless steel archwires. Two brackets of each type were mounted on acrylic blocks with an interbracket distance of 8 mm. For the control group, conventional brackets were ligated using fresh elastomeric modules to ensure consistent ligation force. Tests were conducted in a dry environment using a universal testing machine, applying a 2 N tensile force over 10 mm at 1 mm/min. Kinetic frictional resistance was recorded in Newtons, using new wires for each test. Data were analyzed with Kruskal–Wallis and Mann–Whitney U tests ( P < 0.05). Results: Damon brackets demonstrated the lowest mean kinetic friction (2.57 ± 0.31 N), followed by Smart Clip (2.89 ± 0.21 N), Selfy (2.97 ± 0.17 N), and Control group (3.08 ± 0.31). Differences among groups were significant (H = 42.35, P < 0.001). Pairwise analysis showed Damon produced significantly less friction than Smart Clip, Selfy, and Control group ( P < 0.001), while no difference was observed between Smart Clip and Selfy ( P = 0.094). Conclusion: Bracket design substantially affects frictional resistance. Conventional elastomeric-ligated brackets generate the highest friction. Damon brackets generated significantly lower friction compared with Smart Clip and Selfy, which exhibited similar values. Passive self-ligating systems may therefore enhance biomechanical efficiency, though in vivo validation is warranted.