Dentists have been putting gold crowns and filings in mouths for more than a century; now they could be putting gold sensors on teeth as well.
The technology is called a "tooth tattoo" and it was designed by Princeton nanoscientist Michael McAlpine and Tufts bioengineers Fiorenzo Omenetto, David Kaplan and Hu Tao. It's made of gold, silk and graphite. The sensor would measure the levels of bacteria in the mouth. That can tell dentists whether you're getting closer to developing gum disease.
There are lots of other diseases that show signs in the saliva --AIDS and stomach ulcers are two -- and this is why dentists always ask about your overall health when you go for a cleaning.
The sensor is pretty simple: a layer of gold (the electrode), a layer of graphene and a peptide that bonds with the graphene on one end and bacteria on the other. Supporting the whole thing a layer of silk.
The silk isn't fabric -- it's actually a single strand whose proteins have been altered. Once pressed onto the surface of the tooth, the silk would dissolve and the sensor would be stuck in place. The whole thing would be powered wirelessly.
There are still going to be challenges. This device hasn't been tested in humans -- only on cow teeth. Cows, of course, are much bigger and less likely to complain about a foreign object on their teeth. People, on the other hand, are pretty sensitive, as anyone who has been bothered by a tiny piece of apple skin can attest. So any device will have to be very thin, on the order of micrometers.
Detecting the bacteria will also require a lot of additional work because the peptides necessary to detect bacteria tend to be specific to certain types, and they have to be made from scratch.