Clinical studies have demonstrated that orthodontic appliances impair proper oral hygiene and increase patients susceptibility to carious lesions formation. To improve caries resistance, soluble fluoride has been incorporated into a variety of orthodontic adhesives. Unfortunately, fluoride provides limited anti-microbial function and sustained fluoride release cannot be maintained. In this study, a composite orthodontic adhesive was developed containing a potent antimicrobial compound, benzalkonium chloride (BAC) and its long-term anti-microbial benefits were evaluated. The antimicrobial activities of the modified composite were evaluated using disk diffusion test and bacterial adherence test. Incorporating BAC into a composite resin provided increased antibacterial activity, which was demonstrated by zones of bacterial growth inhibition around the modified composite samples, and reduction of bacterial adherence to composite samples.; The physical properties of the modified material were evaluated using a tensile bond strength and diametral tensile test. The tensile bond strength was evaluated by bonding traction hooks to bovine teeth embedded in acrylic molds using the modified composite. Specimen disks containing 0, 0.75, 1.75, 2.5 wt.% BAC were used in the modified material for the diametral tensile strength test. Data analysis using one-way analysis of variance indicated that there were no significant differences between the modified composite groups and the original product (p 0.05) in both tensile bond strength and the diametral tensile test. In conclusion, the incorporation of benzalkonium chloride to the composite material added antimicrobial properties to the original compound without alteration of its mechanical properties. Bonding orthodontic appliances with these novel adhesives could provide clinically superior performance by inhibiting the growth and adherence of cariogenic pathogens.
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