Effect of Quaternary Ammonium‐Based Antimicrobial Coating on the Mechanical Properties and Bacterial Adhesion to Gummetal Archwire

Objectives: This in vitro study investigated the mechanical and bacterial adhesion properties of Gummetal (GM) orthodontic archwire after application of quaternary ammonium compounds (QACs)–based antimicrobial coating. Methods: Sixty orthodontic archwires were divided into three groups: coated GM (C‐GM) group, consisting of a 0.016 × 0.022‐inch GM core wire coated with QACs, and two control groups—one with a 0.016 × 0.022‐inch uncoated GM wire and the other with a 0.016 × 0.022‐inch stainless steel (SS) wire. The elastic modulus, yield strength, and static friction forces were compared between the C‐GM and control groups. Measurements were conducted using a Dillon Quantrol TC2i universal testing machine. Surface roughness was evaluated using confocal profilometry, and bacterial adhesion was quantified through crystal violet dye staining. Results: The mean elastic modulus for the C‐GM, GM, and SS groups was 6.68 ± 0.1, 6.71 ± 0.2, and 19.7 ± 0.4 GPa, respectively, with significant differences observed between the C‐GM vs. SS and GM vs. SS groups ( p < 0.001). The mean yield strength for the C‐GM, GM, and SS groups was 7.5 ± 0.1, 7.6 ± 0.1, and 19.5 ± 0.2 N, with yield strength being significantly lower in the C‐GM group compared to the GM ( p = 0.036) and SS ( p < 0.001) groups. For friction forces measured within metal brackets, the C‐GM group exhibited a mean friction force of 1.0 ± 0.1 N, which was significantly lower than both the GM (1.1 ± 0.1 N, p = 0.017) and SS (1.2 ± 0.1 N, p < 0.001) groups. Confocal profilometry analysis indicated that the SS group had the lowest surface roughness, followed by GM and then C‐GM. The mean bacterial count for the C‐GM, GM, and SS groups was 0.605, 1.066, and 0.882 AU cm⁻ 1 , respectively, with significant differences observed between each wire pair (adj. p < 0.001). Conclusions: The application of antimicrobial QACs to GM wires effectively reduced friction while preserving their strength and rigidity. Furthermore, the QAC coating demonstrated a significant reduction in bacterial adherence.