Effect of Quaternary Ammonium-Based Antimicrobial Coating on the Mechanical Properties and Bacterial Adhesion to...

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.