The purpose of the study was to investigate the antibacterial efficacy and mechanical properties of experimental orthodontic adhesives containing newly synthesized antibacterial dimethacrylate monomers with doubly charged 1,4-diazabicyclo[2.2.2]octane (DABCO) group (dication).

Experimental orthodontic adhesives were formulated using varying compositions of synthesized antibacterial dimethacrylate monomers containing DABCO dication, C16DC2DMA and BisC11DCDMA, replacing part of the control group, Transbond™XT. The concentrations of monomers tested were 5% C16DC2DMA, 10% C16DC2DMA, 5% BisC11DCDMA, and 10% BisC11DCDMA. The biofilm-inhibition effects of the experimental adhesives against Streptococcus mutans were tested. Brackets were then bonded to extracted human teeth utilizing the experimental adhesives in the bonding protocol. The shear bond strength and modulus of elasticity of the control and experimental groups were tested. The adhesive remnant index scores were recorded.

The experimental adhesives containing 5% or 10% BisC11DCDMA and 10% C16DC2DMA showed significantly lower S. mutans colony forming units (CFU) than the control. Both BisC11DCDMA experimental groups displayed similar mechanical properties as compared to the control, although 10% C16DC2DMA showed a reduction in shear bond strength as compared to the control. For all experimental adhesives, the adhesive remnant index scores were not significantly different compared to the control.

BisC11DCDMA is a novel antibacterial dimethacrylate monomer that exhibits the significant ability to inhibit bacterial growth while maintaining acceptable mechanical properties. When incorporated into orthodontic adhesives, this monomer may reduce the occurrence of white spot lesions around brackets in orthodontic patients.