News in Science

Japanese tooth patch may reduce decay

Scientists have created a microscopically thin film that can coat individual teeth to prevent decay or to make them appear whiter.

The "tooth patch" is a hard-wearing and ultra-flexible material made from hydroxyapatite, the main mineral in tooth enamel that could also mean an end to sensitive teeth.

"This is the world's first flexible apatite sheet, which we hope to use to protect teeth or repair damaged enamel," says Professor Shigeki Hontsu of the Kinki University's Faculty of Biology-Oriented Science and Technology in Japan.

"Dentists used to think an all-apatite sheet was just a dream, but we are aiming to create artificial enamel," the outermost layer of a tooth, he says.

Researchers can create film just 0.004 millimetres thick by firing lasers at compressed blocks of hydroxyapatite in a vacuum to make individual particles pop out.

These particles fall onto a block of salt which is heated to crystallise them, before the salt stand is dissolved in water.

The film is scooped up onto filter paper and dried, after which it is robust enough to be picked up by a pair of tweezers.

"The moment you put it on a tooth surface, it becomes invisible. You can barely see it if you examine it under a light," says Hontsu.

The sheet has a number of minute holes that allow liquid and air to escape from underneath to prevent their forming bubbles when it is applied onto a tooth.

One problem is that it takes almost one day for the film to adhere firmly to the tooth's surface, says Hontsu.

The film is currently transparent but it is possible to make it white for use in cosmetic dentistry.

Researchers are experimenting on disused human teeth at the moment but the team will soon move to tests with animals, says Hontsu, adding he was also trying it on his own teeth.

Five years or more would be needed before the film could be used in practical dental treatment such as covering exposed dentin - the sensitive layer underneath enamel but it could be used cosmetically within three years, says Hontsu.

The technology, which has been jointly developed with Associate Professor Kazushi Yoshikawa of the Osaka Dental University, is patented in Japan and South Korea and applications are under way in the United States, Europe and China.