Squid ink is rich in melanin nanoparticles, and those get trapped in the pockets between your teeth and gums. When a dentist shines a laser onto your mouth, the nanoparticles swell and create pressure differences in the gum pockets. That's where the ultrasound part of the imaging method comes in. Ultrasound can detect those pockets, so dentists can create a full map of your mouth, like this:

[Image credit: Jokerst Bioimaging Lab at UC San Diego. Ultrasound image of the teeth is in black and white. The photoacoustic signal from the squid ink contrast agent in the pocket depth is in red and signals from stains on the teeth are in blue. ]

The result shows how deep those pockets are, which indicate gum health. That's why dentists stick a probe in those pockets to begin with -- if they're only one to two millimeters in depth, it means your gums are healthy. Anything deeper than that is a sign of gum disease, and the deeper those pockets are, the worse the issue is.

Problem is, the results of periodontal probing depend on the amount of pressure a dentist uses and the area he's probing. He could be probing the wrong location or putting too little or too much pressure. Jesse Jokerst, the study's senior author likened the periodontal probe to "examining a dark room with just a flashlight" wherein "you can only see one area at a time." He said that their method is more like "flipping on all the light switches so you can see the entire room all at once," leading to more accurate findings.

The engineers have big plans for their creation, starting with replacing the lasers in the method with more affordable LED lights. Their ultimate goal, however, is to create a mouthpiece that can instantly assess your gum health. They also want to get rid of the the squid ink concoction's salty and bitter taste, though I'll take than any day over painful probing.