A 2013 study of silver nanoparticles, the ones used in true colloidal silver products, examined the effect of the silver against a variety of microorganisms. The researchers found significant effect against common disease-causing bacteria.  Researchers from around the world are currently testing silver nanoparticles for dental use. One study found it helped prevent infection during root canals. 
An Australian study tested silver nanoparticles against bacteria known to worsen rheumatoid arthritis. The study used a silver preparation in a human subject suffering from rheumatoid arthritis. The researchers found it was potent and offered long-lasting protection against irritation associated with the bacteria.