No Shots, No Pain, No Fear

A New Technology Takes on the Dental Drill.

By Mike Martin. Photos by Benjamin Reed.

A recent National Science Foundation grant of more than $250,000 made University of Missouri-Columbia researchers Qingsong Yu and Hao Li two very happy engineers. Soon, perhaps, their good fortune will give us all a reason to smile.

Yu and Li are using the NSF funding to pioneer a dental technology that could take the anxiety out of trips to the dentist's chair. Their new "plasma brush" would replace the dental drill's noisy, sometimes painful spin -- a major cause of dental phobia -- with the silence and serenity of a low-temperature chemical reaction. It should also reduce an enormous waste that bites into nearly every dental practice, the tedious task of replacing failed fillings.

As the researchers envision it, the plasma brush will look much like its low-tech counterpart, the toothbrush, but with a slightly larger handle "hooked up to a few tucked-away gas tanks," Li says.

The new brush, Yu adds, will "save healthy tissue," which takes a beating from "mechanical drilling and acid etching in conventional preparation of cavities."

Clinical trials can't start soon enough for New York City-based cosmetic and reconstructive dentist Daniel Noor, whose Park Avenue practice already employs the latest in laser instrumentation.

"I am a firm believer in great technology," Noor says. "The plasma brush makes a lot of sense -- no shots, no drills, no pain, no fear. Though it's so unique most dentists have never heard of it, I would certainly use it after FDA approval."

Plasmas - electrically conductive gases packed with free-floating electrons - are the most abundant forms of matter in the universe. They swirl into clouds that condense into stars and power the fluorescent bulbs that flash across the Las Vegas night. Lightning, the Aurora Borealis and flat-panel television displays are some of the plasmas in our midst.

After working for years to develop a low-cost way to clean contaminated surfaces, Yu and Li -- both assistant professors of mechanical and aerospace engineering -- used argon gas to create a "plasma tip" shaped much like a tiny scrub brush.

Like the ethereal flame that dances at the tip of a welder's torch, their plasma brush operates at atmospheric pressure, a relatively new feature important for clinical applications.

"Non-thermal plasmas were formerly produced at reduced pressure using an expensive vacuum system that limited their biomedical applications," explains Yu. "Now, they can be operated in open air."

Plasma-treated tissues also remain free from thermal damage, Yu says. This is because their plasma brush is engineered to operate at a cool 42 degrees Celsius, about room temperature, making it an ideal disinfectant. There is no heat and no harmful chemicals.

Far less ideal is a typical filling procedure, during which a dentist drills away the infected material from a decayed tooth, preparing the cavity for the polymer-ceramic composite that will fill it. Drilling disturbs microscopic nerve endings at the center of the tooth, called "pulp," Noor explains. Heat from friction, he adds, expands fluid inside "dentinal tubules," pressuring the nerves even more.

Dispensing with those anxiety provocateurs, the plasma brush not only kills bacteria, but also "modifies the surface of the tooth," Li says, improving its ability to bond with the composite. "Most composites are made of polymers and ceramic. They last, on average, 5 to 8 years before they shrink and break," after which bacteria, acids, and enzymes infiltrate and cause more decay. "The plasma brush should greatly improve the bond and eliminate those problems," says Li.

Noor seconds this opinion, noting that the plasma brush won't leave the "smear layer," a normal residue from traditional drilling that also hampers tooth-to-filling adhesion.

Born in feixian, Shandong Province, on China's eastern coast, Hao Li, now 32, completed both bachelor's and master's degrees in materials science at Xi'an Jiaotong University. He decided to pursue advanced studies in the U.S. because, Li says, "it has the best educational system in the world" and the benefits of advanced dentistry. "There were no dentists in China. No annual cleaning, no floss, and plenty of decay," he says.

A doctoral student at Steven-s Institute of Technology in Hoboken, N.J., Li studied biomaterials of every stripe. He says "collaborative conversations" with Yu, the project's 43-year-old principal investigator, and bioengineer Yong Wang inspired his interest in a better way to fill teeth.

Wang, who directs the craniofacial bioengineering program at the University of Missouri-Kansas City, says that the nation's dentists each year spend close to 75 percent of their time restoring failed fillings, procedures that cost patients nearly $70.3 billion in 2002, the last year data were available.

With the plasma brush, Wang says, "dental restorations could be significantly improved."

Though exciting news for the future, don't expect to see a plasma brush at your next dental appointment, cautions prosthodontist Glenn Wolfinger, co-director of the Institute For Facial Esthetics in Fort Washington, Pa.

"While the research is very interesting, a well-controlled multi-center study by respected clinicians will need to be published in a peer reviewed scientific journal," Wolfinger advises. "Many technologies have come along in the past 20 years promising to replace the dental drill and improve composite bonds. But none has yet had a significant impact."

Li is aware that success will involve more than a technological triumph. But rather than focusing on "exact clinical applications," Li says he's perfecting basic processes, like "improving the plasma we are using."

That's as it should be, explains East Setauket, N.Y.-based restorative and cosmetic dentist Terry Shapiro. "The research is in its earliest stages and will be fascinating to watch as it develops," Shapiro says. "In the 25 years that I have been in dental practice, many technologies, including laser dentistry, digital radiology, and composite materials, have revolutionized how we practice."

Most of the estimated 5 percent to 15 percent of adults who suffer from what the Diagnostic and Statistical Manual of Mental Disorders terms odontophobia begin to fear the dentist during childhood. For that reason alone pediatric dentist Santos Cortez, who currently chairs the Long Beach (Calif.) Children's Oral Health Task Force, cheers the prospect of a plasma dental brush.

Citing tooth decay as "the most chronic health problem in children ages 1-17 years," Cortez maintains that more children miss school for problem teeth than for any other reason.

With its ability to reduce fear, the plasma brush "would be wonderful for pediatric dentistry," he adds. "One of the most frightening issues for children is the noise of the drill."

To date, lasers have been the quiet alternative to the 500,000-rpm drills that whir their way into the teeth -- and consciousness -- of the children that Cortez, a past president of the California Society of Pediatric Dentistry, sees every day.

But lasers, Cortez explains, correct only minor to moderate decay and "cannot be used to perform many of the latest treatments." What's more, they do little to improve the composite-tooth bond. As in adult dentistry, this is one of pediatric dentists' "biggest, biggest concerns."

To drive home his point, Cortez relates the 2007 case of 12-year-old Deamonte Driver, a Prince George's County Maryland boy who died earlier this year after an abscessed tooth spread an infection to his brain.

"His mother didn't have the eighty dollars or insurance that would have paid for a simple tooth extraction," Cortez says. "That's how important filling a cavity can be."

Fortunately, "important" doesn't have to mean costly. The plasma brush is "extremely economical," Yu says. "No complicated and expensive equipment is needed." With any budding technology, great economics is one giant step toward widespread adoption. So is good data, and "we have very good preliminary data," Li explains.

This is all good news to Daniel Noor, who prides himself on looking toward the future for "safe, sound, innovative techniques" that will "improve my patients' lives." In 10 years, if all the right factors are in place, use of the plasma brush, Noor says, "could be very widespread."