Eric J Wu

Publications (2)4.88 Total impact

• Article: Effect of water-aging on dentin bond strength and anti-biofilm activity of bonding agent containing new monomer dimethylaminododecyl methacrylate.

  Ke Zhang, Lei Cheng, Eric J Wu, Michael D Weir, Yuxing Bai, Hockin H K Xu
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  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-aging for 6 months on dentin 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 1 day and 6 months at 37°C. Then the dentin 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 (CFU), and lactic acid production. RESULTS: Dentin bond strength showed a 35% loss in 6 months of water-aging 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 1 d 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-aging 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.
  Journal of dentistry 04/2013; · 2.00 Impact Factor
• Article: Dental plaque microcosm biofilm behavior on calcium phosphate nanocomposite with quaternary ammonium.

  Lei Cheng, Michael D Weir, Ke Zhang, Eric J Wu, Sarah M Xu, Xuedong Zhou, Hockin H K Xu
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  ABSTRACT: Half of dental restorations fail in 10 years, with secondary caries as the main reason. Calcium phosphate composites could remineralize tooth lesions. The objectives of this study were to: (1) impart antibacterial activity to a composite with nanoparticles of amorphous calcium phosphate (NACP); and (2) investigate the effect of quaternary ammonium dimethacrylate (QADM) on mechanical and dental plaque microcosm biofilm properties for the first time. The NACP and glass particles were filled into a dental resin that contained bis(2-methacryloyloxy-ethyl) dimethyl-ammonium bromide, the QADM. NACP nanocomposites containing 0%, 7%, 14%, and 17.5% of QADM by mass, respectively, were photo-cured. A commercial composite with no antibacterial activity was used as control. Mechanical properties were measured in three-point flexure. A human saliva microcosm model was used to grow biofilms on composites. Live/dead assay, metabolic activity, colony-forming unit (CFU) counts, and lactic acid production of biofilms on the composites were measured. Increasing QADM mass fraction monotonically reduced the biofilm viability, CFU and lactic acid. Biofilms on NACP nanocomposite with 17.5% QADM had metabolic activity that was 30% that on a commercial composite control (p<0.05). Total microorganisms, total streptococci, and mutans streptococci CFU counts (mean ± sd; n = 6) on composite control was 6-fold those on NACP +17.5% QADM nanocomposite. Composite control had long strings of bacterial cells with normal short-rod shapes, while some cells on NACP-QADM nanocomposites disintegrated into pieces. Adding QADM to NACP did not decrease the composite strength and elastic modulus, which matched (p>0.1) those of a commercial composite without Ca-PO(4) or antibacterial activity. A dental plaque microcosm model was used to evaluate the novel NACP-QADM nanocomposite. The nanocomposite greatly reduced the biofilm viability, metabolic activity and lactic acid, while its mechanical properties matched those of a commercial composite. NACP-QADM nanocomposite with calcium phosphate fillers, good mechanical properties and a strong antibacterial activity may have potential for anti-biofilm and anti-caries restorations.
  Dental materials: official publication of the Academy of Dental Materials 05/2012; 28(8):853-62. · 2.88 Impact Factor