Detecting Decay

Eating too many sweets this holiday season could cause small lesions to develop in your teeth. If undetected by your dentist, these early signs of decay could turn into painful cavities. Now researchers at IDMoS say that they have made a device that uses electrical impedance to identify tooth decay earlier and more accurately than current methods do.

The device, called a CarieScan, sends a small alternating current of energy through a tooth. A sensor on the tip of the instrument measures the tooth’s response to different frequencies, and the results are analyzed by an onboard computer. A color-coded display and a numerical reading alert the dentist of the health of the tooth.

“The technology is leading edge, and the device appears to be the best so far for automated [decay] detection,” says Rick Niederman, the director of the Center for Evidence-Based Dentistry, at the Forsyth Institute, an independent science and health research facility in Boston.

Laser-based techniques are one of the newer methods for detecting tooth decay. Instead of sending out an electrical current, they focus pulses of laser light on the tooth. One type of laser device that has become popular in dentists’ offices is called a Diagnadent. The device is based on light-induced fluorescence. Light beamed on the tooth is absorbed by chemicals from the decay-causing bacteria that have seeped into areas of mineral loss, and then it’s rereleased at a lower energy. The Diagnadent measures the change in wavelength; a higher reading means more decay.

Another technique, being developed at Quantum Dental Technologies, a startup based in Toronto, Canada, uses light waves and thermal radiation. (See “Quantum Detection of Tooth Decay.”)

The problem with laser devices is that they have a high number of false positives because they identify teeth with stains–whether from coffee, tea, or naturally occurring tartar–as decay, says Andrew Hall, an associate professor at the Dundee Dental Hospital and School at the University of Dundee, in the United Kingdom. “And the use of heat may mean that small intra-oral variations in temperature, such as those caused by breathing, could have a profound effect on results,” says Hall.

The device made by IDMoS has the same sensitivity as a laser, but instead of having a 30 to 40 percent false-positive rate in detecting decay, the rate is only 10 percent, says Alasdair Christie, head of development and operations at IDMoS. “Electrical resistance is a direct method of measuring the structure of a tooth because the mineral that is lost in the very early stages of tooth decay is replaced by a liquid, such as saliva in the oral cavity, and that reduces the resistance of the tooth to electricity,” he says.

The CarieScan, which is about the size of an electric toothbrush, works by sending an alternating current of electricity through a tooth at up to 10 different frequencies. By changing the frequency of the signal, researchers are able to examine different depths under the enamel and create a spectrum of impedance points–the higher the impedance, the more sound the tooth. Software built into the device plots and analyzes the spectrum against a predefined map. The map was created from sample tests of both sound and damaged teeth.

The results are displayed to the dentist within seconds, in two different ways. A color-coded display in the shape of a pyramid ranges from green to red, like a traffic light. Green indicates that the tooth is sound and free of any damage; yellow is an intermediate range that means the tooth has some form of damage; and red indicates tooth decay. If the color yellow appears, a screen will display a numerical score from one to ninety-nine; the closer that score is to ninety-nine, the worse the damage.

Before using a CarieScan, a dentist must make sure that her patient’s teeth are dry enough that electricity does not flow around a tooth and into the gums, but not so dry that electricity does not flow at all. In either of those instances, no harm is done to the patient, but the device will short-circuit, and no reading will be displayed.

This is a simple, painless test to detect tooth decay early and give dentists the opportunity to reverse decay or arrest it without having to fill a cavity, says Hall.

Niederman says that the CarieScan is promising, unique, and useful, but he wants more evidence that it can spot significantly more cavities than a dentist can visually, and that such detection would change what is done therapeutically. IDMoS is working on a sensor to get in between teeth, into areas that are hard for dentists to see and where x-rays cannot be used. “If they can do that, they are an absolute winner,” says Hall.

The CarieScan was launched last month in the United Kingdom and Ireland, and it retails for approximately $3,000.