Mechanical Properties and Antimicrobial Performance of Chitosan-Coated Orthodontic Elastomeric Modules

Orthodontic devices can disturb the balance of oral biofilms, increasing plaque accumulation and the risk of oral disease, with elastomeric modules (EMs) particularly prone to bacterial colonization due to their material properties. Surface modifications have been explored to limit microbial growth. This study investigated the mechanical performance, antibacterial effects, and cytocompatibility of chitosan-based coatings applied to EMs. EMs were coated with either chitosan (CS) or chitosan cross-linked with glutaraldehyde (CS-GTA), while uncoated modules served as controls. The coated modules underwent characterization via Fourier transform infrared (FTIR) and Raman spectroscopy and were subjected to tensile testing to evaluate mechanical properties. Antimicrobial activity was determined through colony-forming unit (CFU) counts, and cytocompatibility was assessed using gingival fibroblasts and the MTT assay. Statistical analyses included ANOVA, Tukey, Kolmogorov–Smirnov, and Kruskal–Wallis tests. Raman analysis confirmed characteristic molecular vibrations of the chitosan coatings. Mechanical testing indicated significant differences among materials, with CS-GTA differing notably from controls, as verified by Tukey post hoc analysis; however, yield stress values did not differ significantly. Both coated groups exhibited lower CFU counts compared to uncoated EMs, and cell viability remained high, averaging 85% for CS and 89% for CS-GTA coatings. CS and glutaraldehyde-cross-linked CS coatings were successfully prepared for EMs without compromising their mechanical integrity. Both coatings effectively suppressed bacterial growth, with no significant difference in antibacterial efficacy between the two coating types.