Non-invasive cavity treatment being developed

Friday, February 29, 2008 | 2:00 p.m. CST; updated 5:32 p.m. CDT, Sunday, July 20, 2008
Hao Li, left, and Qingsong Yu, right, stand in front of their lab equipment at MU's School of Engineering. Both studied in China before earning their doctorates in the United States.

University of Missouri researchers are developing a cavity treatment device that would repair cavities without the pain and discomfort of drilling and add years of durability to fillings.

Assistant Professors Qingsong Yu and Hao Li of MU along with associate professor Yong Wang of University of Missouri-Kansas City have been developing the “plasma brush” for over two years.

“We have the brush for research, but not in the form ready for dentists,” Yu said. “We are redesigning and gathering clinical data. It could still be four to five years until you will see it in a dental office.”

For patients who loathe the dentist’s drill, the technology couldn’t come soon enough.

The brush uses plasma, a state of matter similar to the makeup of the sun. The plasma is an ionized form that reacts chemically and can then be used to clean the surface of a cavity-ridden tooth.

Ionization is when an atom acquires a net electrical charge.

The cavity is prepared and ready for filling after exposing the tooth to the ionized plasma for one to two minutes.

“It is a chemical reaction rather then a mechanical one,” Yu said. Because there are no mechanical machines involved, for example a drill, there is no need for anesthesia or other numbing agent.

Along with the destructive factors of the current cavity treatment process, the average filling only lasts six to eight years.

“If a tooth is drilled, over time the hole gets bigger requiring more drilling and larger fillings,” Yu said. “The current dental composite filling only lasts six to eight years on average. With the plasma brush, the bonding between the teeth and fillings would be stronger and last much longer.”

John Purk, associate professor and sectional head of operative dentistry at the University of Missouri-Kansas City, said anything that could expand the life of a tooth restoration would be welcome.

Teeth are made of two layers, enamel and dentin. There are no problems with bonding dental adhesives to enamel, but the dentin underneath the enamel contains many fluid filled tubes. The reason dentists restore a tooth is because it has caries, which is the technical term for decay, Purk said.

“Besides bonding to dentin that contains tubes filled with fluid, it is very difficult to obtain a strong durable bond to carious dentin,” Purk said.

“This plasma brush would alter the dentin and increase the bond strength of the adhesive to carious dentin and also kill the bacteria.”

“The point of this project is to benefit the patient,” Yu said. “There is no sound and the tool is close to body temperature so the patient will not feel it.”

The team received a $270,000 grant to help this research project from the National Science Foundation.

“It is very competitive to get a grant,” Li said.

According to the National Science Foundation Web site, the agency typically funds 11,000 projects out of 40,000 proposals.

On the other hand, the market for this new way of fixing cavities is not very competitive.

“This is a unique idea, and as far as I know nothing like this is being used,” Li said.

Yu and Yixiang Duan, a scientist from the Los Alamos National Laboratory, filed two U.S. Patent applications for the plasma brush. “There is no such machine yet,” Yu said.

Still, Yu hopes that one day this tool could be used as part of a dentist’s standard procedure to increase dental restoration.

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