Evaluation of Antimicrobial Orthodontic Adhesives Incorporating Metal-Organic Frameworks

Orthodontic adhesives are prone to bacterial colonization, leading to demineralization and white spot lesions during orthodontic treatment. Incorporating antimicrobial agents such as metal-organic frameworks (MOFs) into adhesives offers a novel approach to mitigate bacterial growth.

A commercially available orthodontic adhesive was modified by incorporating 5% and 10% weight concentrations of a zirconium-based MOF. Samples were prepared and tested for antimicrobial efficacy against Streptococcus mutans using a zone of inhibition assay and a bacterial colony counting technique. Shear bond strength (SBS) was tested following the ISO/TS 11405 standards. The release of antimicrobial ions from the adhesive was measured over 14 days. Data were analyzed using ANOVA and post hoc tests, with statistical significance set at P < 0.05.

The modified adhesives showed significant antimicrobial activity, with a reduction in bacterial colony counts of 72% and 85% for 5% and 10% MOF concentrations, respectively. The zone of inhibition increased proportionally with MOF concentration. The 5% MOF adhesive exhibited a slight reduction in SBS (mean: 18.2 ± 1.5 MPa) compared to the control (mean: 20.1 ± 1.2 MPa), whereas the 10% MOF adhesive showed a more pronounced decrease (mean: 15.6 ± 1.8 MPa). Ion release profiles indicated sustained antimicrobial activity over the test period.

The incorporation of MOFs into orthodontic adhesives effectively enhances antimicrobial properties while maintaining acceptable mechanical performance at lower concentrations. This innovative approach could help reduce the risk of enamel demineralization during orthodontic treatment.