Influence of Graphene Surface Coating on Frictional Behaviour of Orthodontic Archwires - A Comparative Study

Abstract Background: Friction at the bracket–archwire interface is a key determinant of efficiency in orthodontic sliding mechanics. Excessive friction dissipates applied forces, increases anchorage demand, and prolongs treatment duration. Surface modification of orthodontic archwires using nanomaterials such as graphene has gained attention due to its exceptional tribological and lubricating properties, which may reduce resistance to sliding. Aim: To compare the frictional resistance between conventional stainless steel (SS) and graphene-coated 0.019 × 0.025-inch stainless steel archwires used with different ligation systems under dry and wet conditions. Materials and Methods: This in-vitro experimental study included 120 archwire specimens divided into six groups based on wire type (SS and graphene-coated SS) and ligation method (elastomeric ligatures, stainless steel ligatures, and self-ligating brackets). Graphene coating was deposited using magnetron sputtering with an approximate thickness of 0.49 µm. Frictional resistance was measured using a universal testing machine at a crosshead speed of 10 mm/min under dry and artificial saliva conditions. Static friction was recorded as the peak force from the load–displacement curve. Data were analyzed using one-way ANOVA followed by Tukey HSD post hoc tests. Results: Significant differences were observed among all groups ( P < 0.001). Graphene-coated archwires showed consistently lower friction than conventional SS wires in both environments. The lowest friction was observed with graphene-coated wires in self-ligating brackets (2.25 N), while conventional SS wires demonstrated the highest values. Conclusion: Graphene surface modification significantly reduces friction during orthodontic sliding mechanics and may improve biomechanical efficiency, supporting further clinical investigation.