Abstract
OBJECTIVES: The objectives of this study were to develop bonding agent containing a new antibacterial monomer dimethylaminododecyl methacrylate (DMADDM) as well as nanoparticles of silver (NAg) and nanoparticles of amorphous calcium phosphate (NACP), and to investigate the effects of water-ageing for 6 months on dentine bond strength and anti-biofilm properties for the first time. METHODS: Four bonding agents were tested: Scotchbond Multi-Purpose (SBMP) Primer and Adhesive control; SBMP+5% DMADDM; SBMP+5% DMADDM+0.1% NAg; and SBMP+5% DMADDM+0.1% NAg with 20% NACP in adhesive. Specimens were water-aged for 1d and 6 months at 37°C. Then the dentine shear bond strengths were measured. A dental plaque microcosm biofilm model was used to inoculate bacteria on water-aged specimens and to measure metabolic activity, colony-forming units (CFUs), and lactic acid production. RESULTS: Dentine bond strength showed a 35% loss in 6 months of water-ageing for SBMP control (mean±sd; n=10); in contrast, the new antibacterial bonding agents showed no strength loss. The DMADDM-NAg-NACP containing bonding agent imparted a strong antibacterial effect by greatly reducing biofilm viability, metabolic activity and acid production. The biofilm CFU was reduced by more than two orders of magnitude, compared to SBMP control. Furthermore, the DMADDM-NAg-NACP bonding agent exhibited a long-term antibacterial performance, with no significant difference between 1d and 6 months (p>0.1). CONCLUSIONS: Incorporating DMADDM-NAg-NACP in bonding agent yielded potent and long-lasting antibacterial properties, and much stronger bond strength after 6 months of water-ageing than a commercial control. The new antibacterial bonding agent is promising to inhibit biofilms and caries at the margins. The method of DMADDM-NAg-NACP incorporation may have a wide applicability to other adhesives, cements and composites.