Effect of amorphous calcium phosphate and silver nanocomposites on dental plaque microcosm biofilms

A dental composite containing amorphous calcium phosphate nanoparticles (NACP) was developed that released calcium (Ca) and phosphate (PO(4)) ions and possessed acid-neutralization capability. There has been little study on incorporation of antibacterial agents into calcium phosphate composites. The objective of this study was to investigate the effect of silver nanoparticle (NAg) mass fraction in NACP nanocomposite on mechanical properties and dental plaque microcosm biofilm for the first time. NACP nanoparticles of 116 nm were synthesized via a spray-drying technique. NAg nanoparticles were synthesized using Ag 2-ethylhexanoate and 2-(tert-butylamino)ethyl methacrylate, yielding NAg of particle size of 2.7 nm that were well-dispersed in the resin. Five NACP nanocomposites were fabricated with NAg mass fractions of 0, 0.028, 0.042, 0.088, and 0.175%, respectively. Mechanical properties of NACP nanocomposites containing 0-0.042% of NAg matched those of a commercial composite without antibacterial activity. Live/dead assay of dental plaque microcosm biofilms showed complete coverage with live bacteria on commercial composite. However, there were increasingly more dead bacteria with higher NAg content in the NACP nanocomposite. Colony-forming unit (CFU) counts for total microorganisms, total streptococci, and mutans streptococci for NACP nanocomposite with 0.042% NAg were about 1/4 those of commercial composite. Lactic acid production on NACP nanocomposite with 0.042% NAg was 1/3 that on commercial composite. In conclusion, novel NACP-NAg nanocomposites were developed which possessed good mechanical properties and potent antibacterial properties, with substantially reduced biofilm viability and lactic acid production. Hence, the NACP-NAg nanocomposites are promising for dental restorations with remineralizing and antibacterial capabilities.