Objectives: Calcium and phosphate ion-releasing resin composites are promising for remineralization. However, there has been no report on incorporating antibacterial agents to these composites. The objective of this study was to develop antibacterial and mechanically strong nanocomposites incorporating a quaternary ammonium dimethacrylate (QADM), nanoparticles of silver (NAg), and nanoparticles of amorphous calcium phosphate (NACP). Methods: The QADM, bis(2-methacryloyloxyethyl) dimethylammonium bromide (ionic dimethacrylate-1), was synthesized from 2-(N,N-dimethylamino)ethyl methacrylate and 2-bromoethyl methacrylate. NAg was synthesized by dissolving Ag 2-ethylhexanoate salt in 2-(tert-butylamino)ethyl methacrylate. Mechanical properties were measured in three-point flexure with bars of 2 mm × 2 mm × 25 mm (n = 6). Composite disks (diameter = 9 mm, thickness = 2 mm) were inoculated with Streptococcus mutans. The metabolic activity and lactic acid production of biofilms were measured (n = 6). Two commercial composites were used as controls. Results: Flexural strength and elastic modulus of NACP + QADM, NACP + NAg, and NACP + QADM + NAg matched those of commercial composites with no antibacterial property (p > 0.1). The NACP + QADM + NAg composite decreased the titer counts of adherent S. mutans biofilms by an order of magnitude, compared to the commercial composites (p < 0.05). The metabolic activity and lactic acid production of biofilms on NACP + QADM + NAg composite were much less than those on commercial composites (p < 0.05). Combining QADM and NAg rendered the nanocomposite more strongly antibacterial than either agent alone (p < 0.05). Significance: QADM and NAg were incorporated into calcium phosphate composite for the first time. NACP + QADM + NAg was strongly antibacterial and greatly reduced the titer counts, metabolic activity, and acid production of S. mutans biofilms, while possessing mechanical properties similar to commercial composites. These nanocomposites are promising to have the double benefits of remineralization and antibacterial capabilities to inhibit dental caries.
Bibliographical noteFunding Information:
We thank Dr. L.C. Chow and Dr. L. Sun of the American Dental Association Foundation (ADAF) for discussions, and Dr. Qianming Chen of the West China College of Stomatology for help. We are grateful to Esstech (Essington, PA) and Dr. Sibel A. Antonson at Ivoclar Vivadent (Amherst, NY) for donating the materials. We acknowledge the technical support of the Core Imaging Facility of the University of Maryland Baltimore. This study was supported by NIH R01 grants DE17974 and DE14190 (HX), NIDCR-NIST Interagency Agreement Y1-DE-7005-01 , University of Maryland Dental School, NIST , and West China College of Stomatology .
- Amorphous calcium phosphate
- Antibacterial nanocomposite
- Quaternary ammonium salt
- Silver nanoparticles
- Streptococcus mutans biofilm
- Tooth caries inhibition