You know when you go to the dentist, and they shove that little measuring-stick-like tool up between each of your teeth and the overlapping gum tissue? That tool is known as a periodontal probe, and it's used to check for gum disease. You might not have to put up with it for much longer, however, as scientists at the University of California San Diego have developed a more accurate gum-checking technique that involves rinsing with squid ink instead.

Ordinarily, a periodontal probe is pushed up underneath the gum at the base of each tooth. If the gum tissue is healthy and hasn't shrunk back from the tooth much, the probe won't go very far – perhaps just one or two millimeters. If the tissue has retreated a lot, however, a pocket will have formed between it and the surface of the tooth, allowing the probe to slide significantly further.

Not only is the procedure often painful, sometimes even causing bleeding of the gums, but it's also time-consuming, as each tooth has to be checked individually. Additionally it can be quite subjective, since different dentists will apply different amounts of pressure to the probe, thus getting different readings.

In the new procedure, patients would start by rinsing their mouths with a mixture of commercially available food-grade squid ink, water and cornstarch. Capillary action would cause that liquid to be drawn up into any gum pockets they might have, and stay there even after the rinse has been spat out.

A light source such as a laser pulse or an LED would then be applied to the gums. This would cause light-absorbing melanin nanoparticles in the squid ink to heat up and expand, generating an acoustic signal. That signal would be detected by an ultrasound transducer, creating an image of the pockets.

A standard tooth-brushing would subsequently remove the ink from the gums.

So far, the technology has been successfully tested on a pig model, using a handheld transducer. Ultimately, however, the researchers hope to develop a mouthpiece that would deliver a light signal to all of the teeth at once, and then read all of the acoustic signals at once. In that way, all of the pockets could be imaged simultaneously, and there would be no ambivalence regarding their size or depth.

Clinical trials on humans are now being planned, although the ink mixture may have to be tweaked a little first – it currently tastes quite bitter and salty.

The research is being led by Prof. Jesse Jokerst, and is described in a paper recently published in the Journal of Dental Research.