If you have lousy teeth, this is exciting news. From the May 2, 2012 news item on Nanowerk (I have removed a link),

Scientists using nanotechology at the University of Maryland School of Dentistry have created the first cavity-filling composite that kills harmful bacteria and regenerates tooth structure lost to bacterial decay. [emphasis mine]

Rather than just limiting decay with conventional fillings, the new composite is a revolutionary dental weapon to control harmful bacteria, which co-exist in the natural colony of microorganisms in the mouth, says professor Huakun (Hockin) Xu, PhD, MS. [emphasis mine]

While the possibilities are promising, I find the idea of a weapon in my mouth disconcerting. (They might want to check out their metaphors a little more closely.) Moving on, there’s a little more detail about this new composite  (from the news item),

Fillings made from the School of Dentistry’s new nanocomposite, with antibacterial primer and antibacterial adhesive, should last longer than the typical five to 10 years, though the scientists have not thoroughly tested longevity. Xu says a key component of the new nanocomposite and nano-structured adhesive is calcium phosphate nanoparticles that regenerate tooth minerals. The antibacterial component has a base of quaternary ammonium and silver nanoparticles along with a high pH. The alkaline pH limits acid production by tooth bacteria.

“The bottom line is we are continuing to improve these materials and making them stronger in their antibacterial and remineralizing capacities as well as increasing their longevity,” Xu says.

The new products have been laboratory tested using biofilms from saliva of volunteers. The Xu team is planning to next test its products in animal teeth and in human volunteers in collaboration with the Federal University of Ceara in Brazil.

The folks at the enewsparkforest blog are not quite so sanguine about this dental development as per their May 3, 2012 posting on the topic (I have removed llinks),

A study conducted in 2008 and confirmed by another study in 2009 shows that washing nano-silver textiles releases substantial amounts of the nanosilver into the laundry discharge water, which will ultimately reach natural waterways and potentially poison fish and other aquatic organisms. A study found nanosilver to cause malformations and to be lethal to small fish at various stages of development since they are able to cross the egg membranes and move into the fish embryos. A 2010 study by scientists at Oregon State University and in the European Union highlights the major regulatory and educational issues that they believe should be considered before nanoparticles are used in pesticides.

As Dexter Johnson in his May 3, 2012 posting on his Nanoclast blog (on the Institute for Electrical and Electronics Engineers website) notes,

The researchers are continuing with their animal and human testing with the nanocomposite. Given that some sectors of the public are concerned about the potential risks of silver nanoparticles, they should probably take a look at the issue as part of their research.

This is not unreasonable especially in light of the concern some folks have had over mercury in dental fillings. Sufficient concern by the way to occasion this cautionary note from Health Canada (from the Mercury and Human Health webpage on their website),

Minimizing Your Risk

Elemental mercury from dental fillings does not generally pose a health risk. There is, however, a fairly small number of people who are hypersensitive to mercury. While Health Canada does not recommend that you replace existing mercury dental fillings, it does suggest that when the fillings need to be repaired, you may want to consider using a product that does not contain mercury.

Pregnant women, people allergic to mercury and those with impaired kidney function should avoid mercury fillings. Whenever possible, amalgam fillings should not be removed when you are pregnant because the removal may expose you to mercury vapour. When appropriate, the primary teeth of children should be filled with non-mercury materials.

Side note: I find it interesting that while Health Canada has not banned the use of mercury in fillings, it does advise against adding more mercury-laced fillings to your mouth and/or using them in your children’s primary teeth, if possible.

Getting back to silver nanoparticles in our mouths, I reiterate Dexter’s suggestion.