The Cutting Edge: Computing/Technology/Innovation : Lasering Teeth for a Cavity-Free Future

You brush, you floss, you use fluoride toothpaste and still you get cavities. Ready for something really new? What about laser light? Scientists have found that zapping teeth with very short pulses of low-energy laser light boosts resistance to cavities dramatically. A few dentists are using lasers experimentally to remove the decay caused by cavities, but scientists from the University of Rochester and Eastman Dental Center are looking to use lasers to prevent cavities altogether.

When teeth are formed, some calcium phosphate--the slow-dissolving mineral that is the main material in tooth enamel--is replaced by carbonate, which dissolves easily in acid and leaves teeth prone to cavities. Using a laser tuned to just the right infrared frequency, the University of Rochester researchers heat the surface of the enamel up to 1,000 degrees Celsius for a fraction of a second. The heat momentarily melts the crystalline structure, knocking out some of the decay-prone carbonate molecules.

When the enamel again fuses, it is 70% to 80% more resistant to acids. Using a pulsed laser allows the tooth time to cool so the interior never rises more than a few degrees Celsius. But don’t throw away your dental floss just yet. The technique has so far only been lab-tested on extracted teeth.

When Will We Get There? Would more people use mass transit if they knew exactly when the bus or train would arrive at their stop? Penn State researchers working with Union Switch and Signal Co. think they would. As part of a project funded by the Federal Transit Administration, they are working with inertial navigation systems such as those used in space flight to provide bus or train passengers with useful specifics.

Inertial navigation systems use instruments that measure speed, acceleration and direction. These instruments, along with a computer, are installed on the buses or trains and the information is transmitted--using technology similar to that used in cellular phones--to a central location.

If someone at bus headquarters sees a vehicle is behind, for instance, they could alert the driver or send another vehicle to augment the route.

The Penn State system is currently being tested on a transit-style bus. But the researchers envision a day when any commuter can tap into the computer system and find out where their bus is located and when it will arrive at their stop.

Wrinkle-Free Metal: Wrinkled clothes might be a mere annoyance, but wrinkled sheet metal can pose serious problems, sometimes rendering the material useless. Wrinkling occurs when sheet metal is “pushed into a die” with too little pressure. With too much pressure, the metal tears. Currently, manufacturers have to rely on trial and error to determine the correct pressure.

Now researchers at Ohio State University have found a way to use commercially available light-emitting sensors to detect wrinkles as they begin forming. The sensors monitor the sheet metal while it is being pushed into the die and adjust the pressure accordingly.

The researchers tested their technique using two different methods. In one setup, two fiber-optic sensors each emit a beam of light that strikes the sheet metal and is reflected back to the sensor. If the length of one light beam becomes longer or shorter than the other, that means a wrinkle is beginning to form.

The second method, more precise but bulkier to use, uses a single laser sensor that measures changes on the metal’s surface.