Assessment of A Novel Antimicrobial Chitosan–Graphene Oxide Coating For Orthodontic Wires: A Surface And Biofilm Analysis

Abstract

Background: Fixed orthodontic appliances increase plaque retention and friction at the bracket–wire interface, contributing to enamel demineralization, gingival inflammation, and reduced mechanical efficiency. Functional surface coatings have been proposed to simultaneously reduce biofilm formation and friction, yet few systems demonstrate integrated antimicrobial, surface, and tribological benefits with short-term stability. Objective: To evaluate the effects of a chitosan–graphene oxide (CS–GO) coating on surface characteristics, antibiofilm activity against Streptococcus mutans, frictional resistance, and short-term stability of stainless-steel orthodontic arch wires. Methods: In this laboratory-based experimental study, sixty 0.019 × 0.025-inch stainless-steel wire segments were randomly allocated to uncoated (n = 30) or CS–GO coated groups (n = 30). Surface roughness (Ra), contact angle, biofilm burden (log10 CFU per wire after 48-hour incubation), and frictional resistance were measured (n = 10 per testing stream per group). Statistical comparisons were performed using independent t-tests with 95% confidence intervals and effect sizes. Results: Coated wires showed significantly lower surface roughness (0.24 ± 0.04 µm vs 0.41 ± 0.05 µm; mean difference −0.17 µm; p < 0.001), reduced contact angle (61.2° ± 5.1° vs 83.6° ± 4.8°; −22.4°; p < 0.001), decreased biofilm burden (5.32 ± 0.11 vs 5.94 ± 0.07 log10 CFU; −0.62 log units; ~75.9% reduction; p < 0.001), and lower frictional force (1.62 ± 0.19 N vs 2.34 ± 0.22 N; −0.72 N; p < 0.001). Conclusion: CS–GO coating significantly improved surface smoothness, enhanced hydrophilicity, reduced S. mutans biofilm formation, and lowered frictional resistance under controlled laboratory conditions, supporting its potential as a multifunctional surface modification for orthodontic stainless-steel wires pending clinical validation