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It’s one of the worst parts of a dental checkup — painful probing with sharp instruments to look for signs of gum disease. The time-consuming and sometimes bloody process keeps patients fearful, hygienists frustrated, and dentists worried they might be missing important symptoms.

Now a nanoengineer in San Diego says he’s got a possible solution. It involves imaging gums after patients swish around a mouthful of squid ink.

Jesse Jokerst, a professor at the University of California, San Diego, whose research includes finding new medical uses for ultrasound, was at his dentist getting scraped, poked, and prodded when he realized there just had to be a better way.


“These tools are really old,” he said. “Have you seen a periodontal probe? It’s just a metal stick.”

For decades, the gold standard for measuring periodontal disease has been to use those hook-shaped sticks to measure “pocket depth” — the gaps between the gum and the tooth that deepen in people with disease. The process is not something patients — or dentists — like.


Dr. Arezou Goshtasbi, a dentist who directs the dental hygiene program at Concorde Career College in Garden Grove, Ca., says for now, dental probing is a critical part of any dental exam and necessary to detect gum disesase, which can destroy mouth tissue and lead to tooth loss. But she can tick off a list of reasons she’s unhappy with the probe and would like to see a higher-tech alternative: “It can be painful to the patient, and we could be transmitting bacteria and disease from an unhealthy part of the mouth to a healthy part,” she said. “It’s time-consuming and it’s subjective based on the clinician. And it is not very accurate.”

Worse, she said, some dentists and hygienists who are pressed for time or worried about making patients uncomfortable tend to “spot check” instead of carefully measure areas around each tooth as they should.

Poor readings means deep pockets could be missed, leading to worsening gum disease and tooth loss. “Failure to diagnose is the number one reason for periodontal offices being sued,” she said.

Overworked hygienists are no fans either. You can find blog posts on dental hygiene community boards with titles like “I hate probing.”

In a paper published Thursday in the Journal of Dental Research, Jokerst and colleagues describe a non-invasive method to measure pocket depth using high-resolution photoacoustic ultrasound, which uses a short burst of light from a laser to create acoustical pressure waves.

The ultrasound is used after a swish of squid ink — an extremely dark liquid full of melanin nanoparticles that absorbs a lot of light. When hit with a laser, squid ink in the mouth heats up and swells, creating pressure differences in the gum pockets that the ultrasound can easily detect, Jokerst said.

The work was conducted on pig jaws, but clinical trials in humans are now being planned. The squid ink, which actually comes from the cuttlefish, a close squid cousin, is the same type used in cooking — to make squid ink pasta, for example — so it is safe for consumption. And it does not stain teeth and comes off easily with brushing, Jokerst said.

Jokerst said the ultrasound can create a map of all pockets around every tooth in a fraction of the time it takes for measurements to be done by hand. “It’s the difference between looking in a dark room with a flashlight versus turning on the entire room lights,” he said.

For Goshtasbi, who recently read an advance version of Jokerst’s paper, such technology can’t come soon enough. “To be honest with you, this is so exciting,” she said. “Dentistry is behind, obviously.”

Her field relies heavily on X-rays for the critical images of bone and teeth. But tools to examine soft tissue have indeed lagged.

“Diagnostic ultrasound is used everywhere in the body except for dental tissues,” said Mark Hinders, a professor of applied science at the College of William and Mary who has been developing techniques for dental ultrasound for more than two decades.

The field of ultrasound dental diagnosis got a boost early on from NASA when the agency was trying to find medical uses for the sophisticated ultrasound technology it uses to detect cracks in spacecraft, Hinders said.

But the work has proven challenging, he said, because of the “complicated geometry” of the mouth and the fact that hard tissue (teeth) lies adjacent to soft tissue (gums). The pockets caused by gum disease, a close meshing of soft and hard tissue, have been especially difficult to image, he said.

The research at San Diego, Hinders said, is one of a number of efforts quietly underway that are moving toward ultrasound devices that may one day be more widespread in dental offices. “Ultrasound is coming to dentistry,” he said. “The need is there.”

But he added that much work lies ahead. Even if signals from mouth tissue can be captured by ultrasound, he said, it’s still difficult to develop the artificial intelligence and machine learning that devices need to correctly interpret them.

And they need to be low-cost: Dental economics don’t allow for the pricey diagnostic tools that might be standard in a field such as cardiology.

Jokerst is the first to agree there are big hurdles remaining. Along with conducting trials to make sure the device works as well in humans as it does in pigs, his group is hoping to create a reusable ultrasound mouthpiece that could wirelessly transmit pocket depth data to a patient’s chart.

“That’s a major engineering feat,” he admitted. “It will take years and years.”

His other challenge: improving the taste of his squid ink rinse, which is quite salty and somewhat bitter. But that’s more easily solved. Said Jokerst: “We’re planning to add a lot of mint.”

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